Two Novel Krüppel-associated Box-containing Zinc-finger Proteins, KRAZ1 and KRAZ2, Repress Transcription through Functional Interaction with the Corepressor KAP-1 (TIF1β/KRIP-1)

Abstract

We have isolated two novel Krüppel-like zinc finger proteins containing the evolutionarily conserved Krüppel-associated box (KRAB), KRAZ1 and KRAZ2, and demonstrated that they repress transcription when heterologously targeted to DNA. Their repression activity appeared to be mediated by the putative corepressor KAP-1 (KRAB-associated protein-1), because KRAZ1/2 bind to KAP-1, but KRAB mutants of KRAZ1/2 that are unable to interact with KAP-1 lack repression activity, and KAP-1 has intrinsic repressor activity and potentiates KRAZ1/2-mediated repression. We dissected the KAP-1 protein into a KRAB-interacting domain and a region necessary for repression. Using a mammalian two-hybrid assay, we further demonstrated that KAP-1 deletions lacking repression activity fused to the VP16 transactivation domain strongly activated transcription when coexpressed with KRAZ1. In contrast, VP16-KAP-1 fusions retaining repression activity resulted in repression. These results provide the first evidence that KAP-1 functionally interacts with KRAB in mammalian cells and seems to exert repressor activity in the DNA-bound KRAB-KAP-1 complex, and they further support the hypothesis that KAP-1 functions as a corepressor for the large class of KRAB-containing zinc finger proteins. We have isolated two novel Krüppel-like zinc finger proteins containing the evolutionarily conserved Krüppel-associated box (KRAB), KRAZ1 and KRAZ2, and demonstrated that they repress transcription when heterologously targeted to DNA. Their repression activity appeared to be mediated by the putative corepressor KAP-1 (KRAB-associated protein-1), because KRAZ1/2 bind to KAP-1, but KRAB mutants of KRAZ1/2 that are unable to interact with KAP-1 lack repression activity, and KAP-1 has intrinsic repressor activity and potentiates KRAZ1/2-mediated repression. We dissected the KAP-1 protein into a KRAB-interacting domain and a region necessary for repression. Using a mammalian two-hybrid assay, we further demonstrated that KAP-1 deletions lacking repression activity fused to the VP16 transactivation domain strongly activated transcription when coexpressed with KRAZ1. In contrast, VP16-KAP-1 fusions retaining repression activity resulted in repression. These results provide the first evidence that KAP-1 functionally interacts with KRAB in mammalian cells and seems to exert repressor activity in the DNA-bound KRAB-KAP-1 complex, and they further support the hypothesis that KAP-1 functions as a corepressor for the large class of KRAB-containing zinc finger proteins. A large number of studies on transcriptional factors has revealed that functional domains of many transcriptional factors are modular. They can be structurally and functionally separated into DNA-binding domains and effector (activation or repression) domains. DNA-binding domains can be classified according to common structural motifs, which are well conserved throughout evolution (1Pabo C.O. Sauer R.T. Annu. Rev. Biochem. 1992; 61: 1053-1095Crossref PubMed Scopus (1221) Google Scholar). One of such motifs is the C2H2-type zinc finger repeat that has been estimated to be present in several hundreds of genes, thus being identified as a major family of DNA-binding proteins (2Bellefroid E.J. Lecocq P.J. Benhida A. Poncelet D.A. Belayew A. Martial J.A. DNA. 1989; 8: 377-387Crossref PubMed Scopus (195) Google Scholar, 3Chowdhury K. Deutsch U. Gruss P. Cell. 1987; 48: 771-778Abstract Full Text PDF PubMed Scopus (131) Google Scholar, 4Klug A. Schwabe J.W. FASEB J. 1995; 9: 597-604Crossref PubMed Scopus (533) Google Scholar). The vast majority of the C2H2-type zinc finger proteins (ZFPs) 1The abbreviations used are: ZFP, zinc finger protein; KRAB, Krüppel-associated box; PCR, polymerase chain reaction; nt, nucleotide(s); DBD, DNA-binding domain; HA, hemagglutinin; NLS, nuclear localization signal; 6MT, six repeats of the Myc epitope; AD, activation domain; PAGE, polyacrylamide gel electrophoresis; GST, glutathione S-transferase; TIF, transcriptional intermediary factor. 1The abbreviations used are: ZFP, zinc finger protein; KRAB, Krüppel-associated box; PCR, polymerase chain reaction; nt, nucleotide(s); DBD, DNA-binding domain; HA, hemagglutinin; NLS, nuclear localization signal; 6MT, six repeats of the Myc epitope; AD, activation domain; PAGE, polyacrylamide gel electrophoresis; GST, glutathione S-transferase; TIF, transcriptional intermediary factor. are classified as Krüppel-like on the basis of the fact that they share a highly conserved stretch of seven amino repeats of the zinc finger domain U. A. U. Cell. Full Text PDF PubMed Scopus Google Scholar). In to the DNA-binding of the or of effector domains has been by the lack of amino or structural motifs common effector domains can be according to the amino has been that activation domains are in amino and P.J. 1989; PubMed Scopus Google Scholar, Annu. Rev. Biochem. 1989; PubMed Scopus Google Scholar). is repression of are in or amino U. Full Text PDF PubMed Scopus Google Krüppel-associated box first identified as evolutionarily conserved of amino that has been to be present in of the Krüppel-like E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). is in the of the Krüppel-like that zinc finger domains in and is into and domain E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). several KRAB domains have been to as when heterologously to the U. A. PubMed Scopus Google Scholar, A. U. A. PubMed Scopus Google Scholar, A. PubMed Scopus Google Scholar, 1995; PubMed Scopus Google Scholar). The domain present in KRAB but the is for such transcriptional repression U. A. PubMed Scopus Google Scholar, A. U. A. PubMed Scopus Google Scholar). The KRAB domain is in amino and to into two which thus as a E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). or repression the KRAB domain is highly conserved in a of the Krüppel-like a common amino and a that the KRAB domains in many share a common U. A. PubMed Scopus Google by the and of a novel protein that interacts with KRAB, PubMed Scopus Google Scholar). KAP-1 identified as or P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google to as and to interact with several KRAB domains but with mutants in to repression and to repress transcription when targeted to PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). KAP-1 is a of the of the finger proteins that the finger as finger and by or two and a putative domain PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). the functions of domains are they have been to be in PubMed Scopus Google Scholar, Biochem. Full Text PDF PubMed Scopus Google Scholar). In the KAP-1 a zinc finger finger by a domain to the PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). The finger is in with the and is present in a number of proteins in transcriptional that be in with Biochem. 1995; Full Text PDF PubMed Scopus Google Scholar). The has been identified in several proteins that transcription in the of large or J. 1992; PubMed Scopus Google Scholar, J.W. J.A. Cell. 1992; Full Text PDF PubMed Scopus Google Scholar, P. Biochem. Full Text PDF PubMed Scopus Google Scholar). has been to the the activity of such or to be in with J. 1992; PubMed Scopus Google highly protein to KAP-1 in the the conserved domains is which identified as a putative of the nuclear P. P. J. 1995; PubMed Scopus Google Scholar). to interact with KRAB and repress transcription when to the P. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). KAP-1 and have been to a family of transcriptional intermediary factors and as of transcriptional repression for the large class of KRAB-containing P. J. PubMed Scopus Google Scholar). is evidence that KAP-1 or interacts with KRAB in mammalian cells and the repression in a of the DNA-bound we the and of two novel KRAZ1 and KRAZ2, which repress transcription and interact with We further the functional of KRAZ1/2 with KAP-1 a mammalian two-hybrid on the of the functional domains in results present the first evidence that KAP-1 functionally interacts with KRAB in mammalian cells and that KAP-1 seems to as a corepressor of in the with the DNA-bound KRAB has been to be a that DNA-binding transcriptional exert repression activity by of in many to PubMed Scopus Google Scholar). with the PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google revealed that KAP-1 functions as a corepressor for the large class of because the for KAP-1 interacts in mammalian cells as well as in with several KRAB domains novel we but with KRAB mutants in repression. KAP-1 has intrinsic repressor activity, because KAP-1 transcription when targeted to the of KAP-1 potentiates repression in a on the with KAP-1 seems to exert the repressor activity in a of the DNA-bound KRAB-KAP-1 These further support the that bind to by putative DNA-binding zinc the KAP-1 to the by KRAB and repress transcription PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google demonstrated that amino of KAP-1, which to the are and for the with KRAB in but the region is of the region in the in with KRAB seems to be but The finger is and in but the finger is in but in These results are in with the by P. PubMed Scopus Google that the region of or is but for the with KRAB in a two-hybrid They that the finger of is for the functional the finger is P. PubMed Scopus Google Scholar). the finger is to to the with KRAB in by the in mammalian two-hybrid that activation by is that of the revealed that KAP-1 lacking the finger with VP16-KAP-1 for to and KAP-1 or thus be that a is for the KAP-1 and KRAB in and that the finger region of KAP-1 is necessary for the with such a of KAP-1, which the and the are to be a domain for repression but for repression. can be the or the be for repression in to the the or region to the functional or of the KAP-1 KAP-1 two or repression that are of the or region with the The domain thus be with repression and be the or region be as as the KAP-1 can a complex, and the or is for of KAP-1 into such a that is the of or be a of necessary for of such a have been for the repression P. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). One is the of into a by because in the two-hybrid KAP-1 and to be with and which are of protein that repress transcription by the of or a P. J. PubMed Scopus Google Scholar). we that KAP-1 lacking the putative domain P. J. PubMed Scopus Google repress transcription KAP-1 containing and in with the that a of the domain that the in repression activity in mammalian cells P. J. PubMed Scopus Google Scholar). the of by with to be a of and lack of with in KAP-1 to be the for repression is repression U. Full Text PDF PubMed Scopus Google in which KRAB or KAP-1 interacts in with proteins of the transcription with the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). of evidence support the repression the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). repression is in as in as well as in transcription U. A. PubMed Scopus Google in which the of the be into demonstrated that KRAB is to repress transcription by polymerase and but by polymerase polymerase in mammalian that KRAB repression activity by with for polymerase and transcription by the into a P. PubMed Scopus Google Scholar). are two for and repression U. Full Text PDF PubMed Scopus Google Scholar). repression seems to be because KRAB has been demonstrated to repress transcription a number of polymerase A. PubMed Scopus Google Scholar, P. PubMed Scopus Google and the of transcriptional U. A. PubMed Scopus Google and KRAB is to repress activity in to activated transcription in transcription U. A. PubMed Scopus Google repression has been to is that repression is with of the transcription but by of to the by P. J. Full Text Full Text PDF PubMed Scopus Google seems to be They that intrinsic protein activity for as well as for of and functional of such in transcriptional repression and has activity be further is that repression can be of in the transcription be that repression and repression by are P. PubMed Scopus Google Scholar). The of repression in KAP-1 and P. J. PubMed Scopus Google repression that and a family of transcriptional intermediary factors that a in the of transcription the P. J. PubMed Scopus Google because identified as a protein transcription by the nuclear in P. P. J. 1995; PubMed Scopus Google and to transcription by and Cell. PubMed Google because they share common to repress transcription when targeted to the but to interact with and with the KRAB repressor domains. seems that as or in a on the the or the of of transcription factors that to the is necessary to the and the in repression. In is to the of repression. In the mammalian two-hybrid assay, we demonstrated that repression of transcription by can be to activation when coexpressed with the deletions that the KRAB-interacting domain but repression activity, that deletions as mutants with to the of functional deletions as a in mammalian cells as well as in the of the of transcriptional repression by the large class of and corepressor A large number of studies on transcriptional factors has revealed that functional domains of many transcriptional factors are modular. They can be structurally and functionally separated into DNA-binding domains and effector (activation or repression) domains. DNA-binding domains can be classified according to common structural motifs, which are well conserved throughout evolution (1Pabo C.O. Sauer R.T. Annu. Rev. Biochem. 1992; 61: 1053-1095Crossref PubMed Scopus (1221) Google Scholar). One of such motifs is the C2H2-type zinc finger repeat that has been estimated to be present in several hundreds of genes, thus being identified as a major family of DNA-binding proteins (2Bellefroid E.J. Lecocq P.J. Benhida A. Poncelet D.A. Belayew A. Martial J.A. DNA. 1989; 8: 377-387Crossref PubMed Scopus (195) Google Scholar, 3Chowdhury K. Deutsch U. Gruss P. Cell. 1987; 48: 771-778Abstract Full Text PDF PubMed Scopus (131) Google Scholar, 4Klug A. Schwabe J.W. FASEB J. 1995; 9: 597-604Crossref PubMed Scopus (533) Google Scholar). The vast majority of the C2H2-type zinc finger proteins (ZFPs) 1The abbreviations used are: ZFP, zinc finger protein; KRAB, Krüppel-associated box; PCR, polymerase chain reaction; nt, nucleotide(s); DBD, DNA-binding domain; HA, hemagglutinin; NLS, nuclear localization signal; 6MT, six repeats of the Myc epitope; AD, activation domain; PAGE, polyacrylamide gel electrophoresis; GST, glutathione S-transferase; TIF, transcriptional intermediary factor. 1The abbreviations used are: ZFP, zinc finger protein; KRAB, Krüppel-associated box; PCR, polymerase chain reaction; nt, nucleotide(s); DBD, DNA-binding domain; HA, hemagglutinin; NLS, nuclear localization signal; 6MT, six repeats of the Myc epitope; AD, activation domain; PAGE, polyacrylamide gel electrophoresis; GST, glutathione S-transferase; TIF, transcriptional intermediary factor. are classified as Krüppel-like on the basis of the fact that they share a highly conserved stretch of seven amino repeats of the zinc finger domain U. A. U. Cell. Full Text PDF PubMed Scopus Google Scholar). In to the DNA-binding of the or of effector domains has been by the lack of amino or structural motifs common effector domains can be according to the amino has been that activation domains are in amino and P.J. 1989; PubMed Scopus Google Scholar, Annu. Rev. Biochem. 1989; PubMed Scopus Google Scholar). is repression of are in or amino U. Full Text PDF PubMed Scopus Google Scholar). The Krüppel-associated box first identified as evolutionarily conserved of amino that has been to be present in of the Krüppel-like E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). is in the of the Krüppel-like that zinc finger domains in and is into and domain E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). several KRAB domains have been to as when heterologously to the U. A. PubMed Scopus Google Scholar, A. U. A. PubMed Scopus Google Scholar, A. PubMed Scopus Google Scholar, 1995; PubMed Scopus Google Scholar). The domain present in KRAB but the is for such transcriptional repression U. A. PubMed Scopus Google Scholar, A. U. A. PubMed Scopus Google Scholar). The KRAB domain is in amino and to into two which thus as a E.J. Poncelet D.A. Lecocq P.J. Martial J.A. U. A. PubMed Scopus Google Scholar). or repression the KRAB domain is highly conserved in a of the Krüppel-like a common amino and a that the KRAB domains in many share a common U. A. PubMed Scopus Google Scholar). by the and of a novel protein that interacts with KRAB, PubMed Scopus Google Scholar). KAP-1 identified as or P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google to as and to interact with several KRAB domains but with mutants in to repression and to repress transcription when targeted to PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). KAP-1 is a of the of the finger proteins that the finger as finger and by or two and a putative domain PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). the functions of domains are they have been to be in PubMed Scopus Google Scholar, Biochem. Full Text PDF PubMed Scopus Google Scholar). In the KAP-1 a zinc finger finger by a domain to the PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). The finger is in with the and is present in a number of proteins in transcriptional that be in with Biochem. 1995; Full Text PDF PubMed Scopus Google Scholar). The has been identified in several proteins that transcription in the of large or J. 1992; PubMed Scopus Google Scholar, J.W. J.A. Cell. 1992; Full Text PDF PubMed Scopus Google Scholar, P. Biochem. Full Text PDF PubMed Scopus Google Scholar). has been to the the activity of such or to be in with J. 1992; PubMed Scopus Google Scholar). A highly protein to KAP-1 in the the conserved domains is which identified as a putative of the nuclear P. P. J. 1995; PubMed Scopus Google Scholar). to interact with KRAB and repress transcription when to the P. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar). KAP-1 and have been to a family of transcriptional intermediary factors and as of transcriptional repression for the large class of KRAB-containing P. J. PubMed Scopus Google Scholar). is evidence that KAP-1 or interacts with KRAB in mammalian cells and the repression in a of the DNA-bound In we the and of two novel KRAZ1 and KRAZ2, which repress transcription and interact with We further the functional of KRAZ1/2 with KAP-1 a mammalian two-hybrid on the of the functional domains in results present the first evidence that KAP-1 functionally interacts with KRAB in mammalian cells and that KAP-1 seems to as a corepressor of in the with the DNA-bound KRAB domains. has been to be a that DNA-binding transcriptional exert repression activity by of in many to PubMed Scopus Google Scholar). with the PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google revealed that KAP-1 functions as a corepressor for the large class of because the for KAP-1 interacts in mammalian cells as well as in with several KRAB domains novel we but with KRAB mutants in repression. KAP-1 has intrinsic repressor activity, because KAP-1 transcription when targeted to the of KAP-1 potentiates repression in a on the with KAP-1 seems to exert the repressor activity in a of the DNA-bound KRAB-KAP-1 These further support the that bind to by putative DNA-binding zinc the KAP-1 to the by KRAB and repress transcription PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google demonstrated that amino of KAP-1, which to the are and for the with KRAB in but the region is of the region in the in with KRAB seems to be but The finger is and in but the finger is in but in These results are in with the by P. PubMed Scopus Google that the region of or is but for the with KRAB in a two-hybrid They that the finger of is for the functional the finger is P. PubMed Scopus Google Scholar). the finger is to to the with KRAB in by the in mammalian two-hybrid that activation by is that of the revealed that KAP-1 lacking the finger with VP16-KAP-1 for to and KAP-1 or thus be that a is for the KAP-1 and KRAB in and that the finger region of KAP-1 is necessary for the with such a of KAP-1, which the and the are to be a domain for repression but for repression. can be the or the be for repression in to the the or region to the functional or of the KAP-1 KAP-1 two or repression that are of the or region with the The domain thus be with repression and be the or region be as as the KAP-1 can a complex, and the or is for of KAP-1 into such a that is the of or be a of necessary for of such a have been for the repression P. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). One is the of into a by because in the two-hybrid KAP-1 and to be with and which are of protein that repress transcription by the of or a P. J. PubMed Scopus Google Scholar). we that KAP-1 lacking the putative domain P. J. PubMed Scopus Google repress transcription KAP-1 containing and in with the that a of the domain that the in repression activity in mammalian cells P. J. PubMed Scopus Google Scholar). the of by with to be a of and lack of with in KAP-1 to be the for repression is repression U. Full Text PDF PubMed Scopus Google in which KRAB or KAP-1 interacts in with proteins of the transcription with the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). of evidence support the repression the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). repression is in as in as well as in transcription U. A. PubMed Scopus Google in which the of the be into demonstrated that KRAB is to repress transcription by polymerase and but by polymerase polymerase in mammalian that KRAB repression activity by with for polymerase and transcription by the into a P. PubMed Scopus Google Scholar). are two for and repression U. Full Text PDF PubMed Scopus Google Scholar). repression seems to be because KRAB has been demonstrated to repress transcription a number of polymerase A. PubMed Scopus Google Scholar, P. PubMed Scopus Google and the of transcriptional U. A. PubMed Scopus Google and KRAB is to repress activity in to activated transcription in transcription U. A. PubMed Scopus Google repression has been to is that repression is with of the transcription but by of to the by P. J. Full Text Full Text PDF PubMed Scopus Google seems to be They that intrinsic protein activity for as well as for of and functional of such in transcriptional repression and has activity be further is that repression can be of in the transcription be that repression and repression by are P. PubMed Scopus Google Scholar). The of repression in KAP-1 and P. J. PubMed Scopus Google repression that and a family of transcriptional intermediary factors that a in the of transcription the P. J. PubMed Scopus Google because identified as a protein transcription by the nuclear in P. P. J. 1995; PubMed Scopus Google and to transcription by and Cell. PubMed Google because they share common to repress transcription when targeted to the but to interact with and with the KRAB repressor domains. seems that as or in a on the the or the of of transcription factors that to the is necessary to the and the in repression. In is to the of repression. In the mammalian two-hybrid assay, we demonstrated that repression of transcription by can be to activation when coexpressed with the deletions that the KRAB-interacting domain but repression activity, that deletions as mutants with to the of functional deletions as a in mammalian cells as well as in the of the of transcriptional repression by the large class of and corepressor has been to be a that DNA-binding transcriptional exert repression activity by of in many to PubMed Scopus Google Scholar). with the PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google revealed that KAP-1 functions as a corepressor for the large class of because the for KAP-1 interacts in mammalian cells as well as in with several KRAB domains novel we but with KRAB mutants in repression. KAP-1 has intrinsic repressor activity, because KAP-1 transcription when targeted to the of KAP-1 potentiates repression in a on the with KAP-1 seems to exert the repressor activity in a of the DNA-bound KRAB-KAP-1 These further support the that bind to by putative DNA-binding zinc the KAP-1 to the by KRAB and repress transcription PubMed Scopus Google Scholar, P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). We demonstrated that amino of KAP-1, which to the are and for the with KRAB in but the region is of the region in the in with KRAB seems to be but The finger is and in but the finger is in but in These results are in with the by P. PubMed Scopus Google that the region of or is but for the with KRAB in a two-hybrid They that the finger of is for the functional the finger is P. PubMed Scopus Google Scholar). the finger is to to the with KRAB in by the in mammalian two-hybrid that activation by is that of the revealed that KAP-1 lacking the finger with VP16-KAP-1 for to and KAP-1 or thus be that a is for the KAP-1 and KRAB in and that the finger region of KAP-1 is necessary for the with such a of KAP-1, which the and the are to be a domain for repression but for repression. can be the or the be for repression in to the the or region to the functional or of the KAP-1 KAP-1 two or repression that are of the or region with the The domain thus be with repression and be the or region be as as the KAP-1 can a complex, and the or is for of KAP-1 into such a that is the of or be a of necessary for of such a have been for the repression P. PubMed Scopus Google Scholar, P. J. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). One is the of into a by because in the two-hybrid KAP-1 and to be with and which are of protein that repress transcription by the of or a P. J. PubMed Scopus Google Scholar). we that KAP-1 lacking the putative domain P. J. PubMed Scopus Google repress transcription KAP-1 containing and in with the that a of the domain that the in repression activity in mammalian cells P. J. PubMed Scopus Google Scholar). the of by with to be a of and lack of with in KAP-1 to be the for repression is repression U. Full Text PDF PubMed Scopus Google in which KRAB or KAP-1 interacts in with proteins of the transcription with the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). of evidence support the repression the of P. PubMed Scopus Google Scholar, U. A. PubMed Scopus Google Scholar). repression is in as in as well as in transcription U. A. PubMed Scopus Google in which the of the be into demonstrated that KRAB is to repress transcription by polymerase and but by polymerase polymerase in mammalian that KRAB repression activity by with for polymerase and transcription by the into a P. PubMed Scopus Google Scholar). are two for and repression U. Full Text PDF PubMed Scopus Google Scholar). repression seems to be because KRAB has been demonstrated to repress transcription a number of polymerase A. PubMed Scopus Google Scholar, P. PubMed Scopus Google and the of transcriptional U. A. PubMed Scopus Google and KRAB is to repress activity in to activated transcription in transcription U. A. PubMed Scopus Google Scholar). The repression has been to is that repression is with of the transcription but by of to the by P. J. Full Text Full Text PDF PubMed Scopus Google seems to be They that intrinsic protein activity for as well as for of and functional of such in transcriptional repression and has activity be further is that repression can be of in the transcription be that repression and repression by are P. PubMed Scopus Google Scholar). The of repression in KAP-1 and P. J. PubMed Scopus Google repression that and a family of transcriptional intermediary factors that a in the of transcription the P. J. PubMed Scopus Google because identified as a protein transcription by the nuclear in P. P. J. 1995; PubMed Scopus Google and to transcription by and Cell. PubMed Google because they share common to repress transcription when targeted to the but to interact with and with the KRAB repressor domains. seems that as or in a on the the or the of of transcription factors that to the is necessary to the and the in repression. In is to the of repression. In the mammalian two-hybrid assay, we demonstrated that repression of transcription by can be to activation when coexpressed with the deletions that the KRAB-interacting domain but repression activity, that deletions as mutants with to the of functional deletions as a in mammalian cells as well as in the of the of transcriptional repression by the large class of and corepressor We are to K. and for and and We for of the We for