Kruppel-like Factor 4 (KLF4) Represses Histidine Decarboxylase Gene Expression through an Upstream Sp1 Site and Downstream Gastrin Responsive Elements

Abstract

Histidine decarboxylase (HDC) is the enzyme that catalyzes the conversion of histidine to histamine, a bioamine that plays an important role in allergic responses, inflammation, neurotransmission, and gastric acid secretion. Previously, we demonstrated that gastrin activates HDC promoter activity in a gastric cancer (AGS-E) cell line through three overlapping downstream promoter elements. In the current study, we used the yeast one-hybrid strategy to identify nuclear factors that bind to these three elements. Among eight positives from the one-hybrid screen, we identified Kruppel-like factor 4 (KLF4) (previously known as gut-enriched Kruppel-like factor (GKLF)) as one factor that binds to the gastrin responsive elements in the HDC promoter. Electrophoretic mobility shift assays confirmed that KLF4 is able to bind all three gastrin responsive elements. In addition, transient cotransfection experiments showed that overexpression of KLF4 dose dependently and specifically inhibited HDC promoter activity. Regulation of HDC transcription by KLF4 was confirmed by changes in the endogenous HDC messenger RNA by KLF4 small interfering RNA and KLF4 overexpression. We further showed that KLF4 inhibits HDC promoter activity by competing with Sp1 at the upstream GC box and also independently by binding the three downstream gastrin responsive elements. Taken together, these results indicate that KLF4 can act to repress HDC gene expression by Sp1-dependent and -independent mechanisms. Histidine decarboxylase (HDC) is the enzyme that catalyzes the conversion of histidine to histamine, a bioamine that plays an important role in allergic responses, inflammation, neurotransmission, and gastric acid secretion. Previously, we demonstrated that gastrin activates HDC promoter activity in a gastric cancer (AGS-E) cell line through three overlapping downstream promoter elements. In the current study, we used the yeast one-hybrid strategy to identify nuclear factors that bind to these three elements. Among eight positives from the one-hybrid screen, we identified Kruppel-like factor 4 (KLF4) (previously known as gut-enriched Kruppel-like factor (GKLF)) as one factor that binds to the gastrin responsive elements in the HDC promoter. Electrophoretic mobility shift assays confirmed that KLF4 is able to bind all three gastrin responsive elements. In addition, transient cotransfection experiments showed that overexpression of KLF4 dose dependently and specifically inhibited HDC promoter activity. Regulation of HDC transcription by KLF4 was confirmed by changes in the endogenous HDC messenger RNA by KLF4 small interfering RNA and KLF4 overexpression. We further showed that KLF4 inhibits HDC promoter activity by competing with Sp1 at the upstream GC box and also independently by binding the three downstream gastrin responsive elements. Taken together, these results indicate that KLF4 can act to repress HDC gene expression by Sp1-dependent and -independent mechanisms. Histamine is a bioamine that plays an important role in many physiological processes, including allergy, inflammation, neurotransmission, and gastric acid secretion (1Rangachari P.K. Am. J. Physiol. 1992; 262: G1-G13PubMed Google Scholar, 2Barocelli E. Ballabeni V. Pharmacol. Res. 2003; 47: 299-304Crossref PubMed Scopus (32) Google Scholar, 3Gelfand E.W. Am. J. Med. 2002; 113: 2S-7SAbstract Full Text Full Text PDF PubMed Google Scholar). Histidine decarboxylase (HDC) 1The abbreviations used are: HDC, histidine decarboxylase; KLF, Kruppel-like factor; ODC, ornithine decarboxylase; 3-AT, 3-aminotrizole; EMSA, electrophoretic mobility shift assay; siRNA, small interfering RNA; GAS-RE, gastrin responsive elements; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.1The abbreviations used are: HDC, histidine decarboxylase; KLF, Kruppel-like factor; ODC, ornithine decarboxylase; 3-AT, 3-aminotrizole; EMSA, electrophoretic mobility shift assay; siRNA, small interfering RNA; GAS-RE, gastrin responsive elements; GAPDH, glyceraldehyde-3-phosphate dehydrogenase. is the single enzyme that converts histidine to histamine (4Medina M.A. Quesada A.R. Nunez de Castro I. Sanchez-Jimenez F. Biochem. Pharmacol. 1999; 57: 1341-1344Crossref PubMed Scopus (80) Google Scholar). HDC is expressed in many different cell types, including mast cells, skin cells, platelets, and basophils. However, in the adult mammals, HDC is highly expressed in enterochromaffin-like cells, where the HDC activity is tightly regulated by a gut peptide hormone, gastrin (5Hocker M. Zhang Z. Koh T.J. Wang T.C. Yale J. Biol. Med. 1996; 69: 21-33PubMed Google Scholar). HDC regulation occurs at both the transcriptional and post-translational levels, the latter by proteolytic processing through the ubiquitin-proteasome pathway (6Fleming J.V. Wang T.C. J. Biol. Chem. 2003; 278: 686-694Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 7Hirasawa N. Murakami A. Ohuchi K. Eur. J. Pharmacol. 2001; 418: 23-28Crossref PubMed Scopus (23) Google Scholar). HDC promoter activity is up-regulated by several different stimuli, including gastrin (8Zhang Z. Hocker M. Koh T.J. Wang T.C. J. Biol. Chem. 1996; 271: 14188-14197Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar), phorbol ester phorbol 12-myristate 13-acetate (8Zhang Z. Hocker M. Koh T.J. Wang T.C. J. Biol. Chem. 1996; 271: 14188-14197Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 9Hocker M. Henihan R.J. Rosewicz S. Riecken E.O. Zhang Z. Koh T.J. Wang T.C. J. Biol. Chem. 1997; 272: 27015-27024Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar, 10Hocker M. Zhang Z. Fenstermacher D.A. Tagerud S. Chulak M. Joseph D. Wang T.C. Am. J. Physiol. 1996; 270: G619-G633Crossref PubMed Google Scholar, 11Ohgoh M. Yamamoto J. Kawata M. Yamamura I. Fukui T. Ichikawa A. Biochem. Biophys. Res. Commun. 1993; 196: 1113-1119Crossref PubMed Scopus (18) Google Scholar), oxidative stress (12Hocker M. Rosenberg I. Xavier R. Henihan R.J. Wiedenmann B. Rosewicz S. Podolsky D.K. Wang T.C. J. Biol. Chem. 1998; 273: 23046-23054Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar), thrombopointin (13Pacilio M. Debili N. Arnould A. Machavoine F. Rolli-Derkinderen M. Bodger M. Arock M. Dumenil D. Dy M. Schneider E. Biochem. Biophys. Res. Commun. 2001; 285: 1095-1101Crossref PubMed Scopus (9) Google Scholar), and Helicobacter pylori infection (14Wessler S. Rapp U.R. Wiedenmann B. Meyer T.F. Schoneberg T. Hocker M. Naumann M. FASEB J. 2002; 16: 417-419Crossref PubMed Scopus (38) Google Scholar, 15Wessler S. Hocker M. Fischer W. Wang T.C. Rosewicz S. Haas R. Wiedenmann B. Meyer T.F. Naumann M. J. Biol. Chem. 2000; 275: 3629-3636Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar). Whereas not all of the cis-acting DNA elements or the transcriptional factors involved in regulation of HDC transcription have been identified, three GC-rich gastrin responsive elements located downstream of the transcription initiation site have been characterized in the human HDC promoter region (16Raychowdhury R. Fleming J.V. McLaughlin J.T. Bulitta C.J. Wang T.C. Biochem. Biophys. Res. Commun. 2002; 297: 1089-1095Crossref PubMed Scopus (21) Google Scholar, 17Raychowdhury R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar). Through the use of Southwestern blot and UV cross-linking, the sizes of the three gastrin responsive element-binding factors have previously been assessed at 53, 33, and 110 kDa of apparent molecular mass, respectively (16Raychowdhury R. Fleming J.V. McLaughlin J.T. Bulitta C.J. Wang T.C. Biochem. Biophys. Res. Commun. 2002; 297: 1089-1095Crossref PubMed Scopus (21) Google Scholar, 17Raychowdhury R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar). Recently, a neural peptide pituitary adenylate cyclase-activating polypeptide has been reported to regulate HDC promoter activity in PC12 cells, and the responsive element of pituitary adenylate cyclase-activating polypeptide has been further mapped to the –177 to –170 region of the HDC promoter. Moreover, by using different protein kinase inhibitors, it has been shown that the mechanism of pituitary adenylate cyclase-activating polypeptide regulation is distinct from gastrin regulation of the HDC promoter (18McLaughlin J.T. Ai W. Sinclair N.F. Colucci R. Raychowdhury R. Koh T.J. Wang T.C. Am. J. Physiol. 2004; 268: G51-G59Google Scholar). Interestingly, the DNA of the HDC promoter region has been also shown to HDC gene expression in both the human and S. K. A. E. S. K. K. T. Res. 2000; PubMed Scopus Google Scholar, A. S. T. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). HDC promoter region was in the cell as the mast cell line and the cell line In HDC expression as the HDC promoter was also through of in the of and expression of HDC in S. K. A. E. S. K. K. T. Res. 2000; PubMed Scopus Google Scholar). of the GC box in the human HDC promoter to the promoter Sp1 binding to GC box element not to by DNA at site A. S. T. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). has also been shown to gene expression through GC-rich DNA in the promoter. of the promoter was by a binding site M. Raychowdhury R. T. Wiedenmann B. Rosewicz S. Wang T.C. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). In addition, gastrin has been shown to the promoter through a binding site M. N. E. R. E. T. Hocker M. 2001; PubMed Scopus Google Scholar). gastrin responsive elements in the HDC promoter also and bind transcription Whereas of these gastrin responsive elements not with In of transcription factors that bind to GC Sp1 was the transcriptional factor to J.T. R. Full Text PDF PubMed Scopus Google Scholar), and it binds to GC D. J.T. K. R. PubMed Scopus Google Scholar), B. A. R. S. Biochem. Biophys. Res. Commun. PubMed Scopus Google Scholar), as as transcription elements K. K. K. A. M. J. 1992; PubMed Scopus Google Scholar). Sp1 to the of transcriptional factors at identified in A.R. J. J. Physiol. 2001; PubMed Scopus Google Scholar), including the Sp1 Kruppel-like factors and with at with three that to in the all factors to bind with to GC-rich all have the to Kruppel-like factor 4 previously known as gut-enriched Kruppel-like is a transcriptional factor in the de B. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar, R.J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google and in human M. Wang M.A. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar), binds GC-rich DNA with a DNA binding of Res. 1998; PubMed Scopus Google Scholar). is a of the that at and is highly expressed in the and A.R. J. J. Physiol. 2001; PubMed Scopus Google Scholar). has been demonstrated by different that KLF4 both activates and gene transcription J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google Scholar, J. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar, D. Kawata M. K. Res. 2002; PubMed Google Scholar, Z. N. B. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar), and these and have also been mapped KLF4 M. Wang M.A. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar, Res. 2000; PubMed Google Scholar). of KLF4 the of KLF4 in of cell and of in of ornithine decarboxylase promoter activity J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google and of several J. J. 2003; PubMed Scopus Google Scholar, J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar, J. 2000; PubMed Scopus Google Scholar). In addition, is a KLF4 in cell DNA J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar), and a KLF4 in the of in the N. 2002; PubMed Google Scholar). In addition, using a gastric KLF4 that KLF4 is gastric and N. of Scholar). In study, we used yeast one-hybrid to identify KLF4 as one of the gastrin responsive element binding In addition, we also demonstrated that overexpression of KLF4 and specifically inhibits HDC promoter and the KLF4 the promoter is through both upstream Sp1 binding GC box and downstream gastrin responsive elements. one-hybrid was to the of the gastrin responsive element to as gastrin responsive elements with and at the upstream of the with and was further yeast to the of was by with was by human from the from the yeast in with F. 57: PubMed Scopus Google Scholar). from these and with yeast one-hybrid three of three gastrin responsive element the to yeast using the strategy as from the and to to and to using strategy A.R. PubMed Scopus Google Scholar). yeast from with different of of yeast to 4 in a and Electrophoretic from was by the of Res. PubMed Scopus Google Scholar), as by A. PubMed Scopus Google Scholar). of as shown in and using enzyme and DNA was by one with that has of nuclear from with of or Sp1 binding GC and different of or in a and W. E. A. J. 1999; PubMed Google Scholar). to the of of further a and was at at 4 was and to a and the was using a of HDC with and by different HDC promoter with and at the and with with the HDC promoter by with the as in also have in the to further used as the to the as using the with and enzyme at the as in I. all confirmed by used HDC promoter to in a human and expression as RNA was from as transcription was to the was used as to using the and and and and and was with and with and all confirmed by and and in and in a by of with the using to the to in was with of kinase expression as an of different HDC and of the different expression or the was with the with gastrin a gastrin is not the in RNA from and to in a or a of KLF4 and with KLF4 from or KLF4 expression and the to the with the DNA to RNA was using in with the of RNA was used as a to the using the from was used in and using the of human and the HDC and the KLF4 and and the of the of and of the of human HDC used as the to the with of RNA and HDC and to using a from and a with the was and to a and the was using a assays with of HDC with or with and at at to the of cell to and with of with of the cell was in a of by of the to the promoter activity. overexpression and the as the and with and the was by of protein was and the to was using and by a to identify the nuclear factors that bind the gastrin responsive elements in the HDC a human was using of as the that from to in the promoter from the of further confirmed by using the gastrin responsive elements and shown in shown in of the from not from showed cell the 3-AT, showed that protein expressed from can bind all three gastrin responsive elements is not a the from was to the of the human KLF4 the yeast one-hybrid in to KLF4 we of and by gene We to in transcriptional factor is highly expressed in the and inhibits promoter activity J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google Scholar), an enzyme that is the as KLF4 by we identified KLF4 as a factor binding to we confirmed through shown in was and with nuclear from cells, and the was a and and of different used as in shown in with the to a with 4 and to by these In addition, with the to a the a DNA binding in the gene promoter K. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google that binds to KLF4 as previously reported D. Kawata M. K. Res. 2002; PubMed Google Scholar). that KLF4 is in the of KLF4 in was confirmed by with a KLF4 in was not a highly transcriptional factor Sp1 was used from the we have shown using both KLF4 binding and that KLF4 binds experiments using and as in and also showed that KLF4 is able to bind both and of and with nuclear in and one was and by not with the KLF4 in a and the of KLF4 and the HDC it has been reported that KLF4 can act as a transcriptional and in different M. Wang M.A. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar, Res. 1998; PubMed Scopus Google Scholar, J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google Scholar, J. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar, D. Kawata M. K. Res. 2002; PubMed Google Scholar). In addition, KLF4 is highly expressed in of the KLF4 binds to the HDC promoter as demonstrated by yeast one-hybrid and it was of to the of KLF4 binding HDC gene the transcriptional activity of KLF4 the HDC promoter the HDC promoter gene was in the HDC promoter from to to the transcriptional initiation site by and an upstream an upstream GC and the three downstream gastrin responsive elements. the of KLF4 HDC promoter transient cotransfection experiments with the HDC and of KLF4 expression shown in KLF4 inhibited HDC promoter with with of KLF4 KLF4 was further the activity of the the human HDC promoter (8Zhang Z. Hocker M. Koh T.J. Wang T.C. J. Biol. Chem. 1996; 271: 14188-14197Abstract Full Text Full Text PDF PubMed Scopus (42) Google by cotransfection with the KLF4 expression or the to the HDC KLF4 also inhibited the promoter activity of the HDC the activity of the promoter was the promoter the of the the of KLF4 both was we used the HDC promoter further has previously been that KLF4 is a of the Kruppel-like and three at the also as Kruppel-like is the Kruppel-like factor to the of the KLF4 the HDC both and KLF4 expression with the HDC promoter Whereas was in with KLF4 was in promoter activity with expression In addition, was the KLF4 acid from to or the acid from to used of KLF4 or with that the of KLF4 is of the M. Wang M.A. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). results with that and KLF4 have different transcriptional (8Zhang Z. Hocker M. Koh T.J. Wang T.C. J. Biol. Chem. 1996; 271: 14188-14197Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar), and further confirmed that the HDC promoter was inhibited specifically by to that of the in of the KLF4 was confirmed of KLF4 protein expressed in the HDC by KLF4 further the regulation of the HDC promoter activity by the endogenous HDC messenger RNA was endogenous KLF4 shown in endogenous KLF4 messenger RNA was by siRNA, and was by KLF4 overexpression as the endogenous HDC was up-regulated by KLF4 and by KLF4 overexpression with results with gene was further that the of the endogenous KLF4 by with a of endogenous HDC In addition, overexpression of KLF4 results in of KLF4 not with the of endogenous HDC Moreover, of KLF4 by the HDC by using RNA further the of of the HDC transcription by Sp1 HDC through GC has been reported that one of the mechanism by KLF4 inhibits gene expression is through with transcriptional as bind GC-rich J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google Scholar). In the HDC promoter is a GC-rich region with to the Sp1 binding Sp1 binding with GC box was shown by using Sp1 in the of Sp1 in HDC promoter activity was not A. S. T. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). further the binding of Sp1 with using the as the the GC box with at both and In the of three and in that these to with in the GC box with these with 4 the Sp1 with these the Sp1 that Sp1 or one of as and is in these of Sp1 in the was further confirmed by of and a using the a not the of the of and and in using in the that the is in these However, overexpression of the not HDC promoter activity not that the of Sp1 and can bind DNA is with the previously reported F. N. S. R. C.J. 2000; PubMed Scopus Google Scholar). these results the binding of Sp1 with the upstream GC box in the HDC promoter. further the of Sp1 binding with the GC box the HDC an Sp1 expression was with a HDC promoter of the Sp1 expression HDC promoter activity was However, in the of GC box in the HDC previously shown to Sp1 binding by HDC promoter activity as as HDC promoter was that Sp1 HDC promoter activity through binding with the upstream GC was further confirmed by the of endogenous HDC Sp1 overexpression using RNA assays 4 KLF4 with Sp1 in Regulation of HDC an promoter activity by overexpression of KLF4 and Sp1 a mechanism in regulation of the HDC promoter. further cotransfection of the Sp1 and KLF4 expression with the HDC the Sp1 was to of KLF4 inhibited HDC promoter In in cotransfection experiments where the of KLF4 expression was Sp1 was able to dose dependently HDC promoter cotransfection experiments further the of Sp1 and KLF4 in transcriptional GC in HDC KLF4 KLF4 with Sp1 in the regulation of HDC promoter and Sp1 activates the promoter activity through the upstream GC it is that GC box also KLF4 is the GC box from the HDC promoter was an promoter and the of overexpression of the KLF4 was using transient cotransfection shown in the activity as was by the of the GC box the Sp1 of Sp1 binds DNA element in transcriptional was by the in the GC further the of GC was promoter KLF4 with was the KLF4 with the GC promoter in the GC box the indicate that the GC box in the HDC promoter can also and that is KLF4 HDC through KLF4 binds all three downstream gastrin responsive elements by the of KLF4 binding to was HDC with the upstream Sp1 binding site as in to through of three downstream gastrin responsive elements or in or as and in experiments with these different HDC and KLF4 expression or the Among the different HDC was in in the promoter activity the was with the the was the with in both and with the Sp1 showed activity. However, in the of Sp1 binding site was by single or in Interestingly, the KLF4 was the promoter activity was not by these the by KLF4 the HDC promoter activity an upstream Sp1 site that KLF4 is able to HDC promoter activity in both Sp1-dependent and -independent KLF4 and of HDC have been shown by to HDC promoter (8Zhang Z. Hocker M. Koh T.J. Wang T.C. J. Biol. Chem. 1996; 271: 14188-14197Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar, 17Raychowdhury R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar). In study, KLF4 was shown to bind to the and to HDC promoter activity. we the gastrin and experiments in with the KLF4 expression and the different HDC in the Sp1 binding GC box and in gastrin responsive elements with gastrin or HDC promoter was by in not as previously reported R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar). was by in all of the HDC responsive to gastrin with the the gastrin Taken together, these results that and of the HDC promoter activity by mechanisms. In study, we yeast one-hybrid to identify a transcription factor highly expressed in the with a molecular of as one of the nuclear factors that binds to the in the HDC promoter. molecular of KLF4 to that it was a the binding protein R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar), further and that KLF4 in binds all three gastrin responsive elements. experiments showed that KLF4 dose dependently and specifically HDC promoter activity and endogenous HDC expression was also regulated by In cotransfection and promoter a of Sp1 and KLF4 in regulation of HDC gene in the HDC promoter that to gastrin that gastrin regulation and KLF4 HDC promoter results in that KLF4 inhibits HDC promoter activity by with Sp1 at the upstream GC is with that KLF4 promoter M. Res. 2000; PubMed Google Scholar), promoter J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus (62) Google Scholar), and promoter W. K. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google through an Sp1-dependent However, it has also been reported that KLF4 can gene transcription in with Sp1 and KLF4 have been reported to the promoter D. Kawata M. K. Res. 2002; PubMed Google and the promoter J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). transcriptional with the known of KLF4 to by that cell and as and and to expression of as 4 and the activity of KLF4 different have to with in of the that in the as in ODC, and both Sp1 and KLF4 one binding in the Sp1 and KLF4 binding as in and KLF4 gene transcription by competing with Sp1 one binding in the of binding KLF4 is able to gene expression in with In the HDC promoter region is an Sp1 binding GC and is KLF4 binding site in the as However, the that KLF4 also binds to three downstream that to the binding not all Through with the Sp1 binding KLF4 gene transcription by the of the Sp1 transcriptional to the promoter In to with Sp1 binding to the HDC KLF4 transcriptional through several mechanisms. Sp1 and KLF4 has been shown by Zhang W. K. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). the of the transcriptional as the gene transcriptional S. S. R. 1999; PubMed Scopus Google Scholar), in transcriptional KLF4 also with the to of the of the to the Sp1 binding site or to the of the activity of the that all of these not and further experiments to to these also demonstrated that KLF4 inhibits HDC promoter activity in an through the downstream of to HDC gene regulation by KLF4 promoter activity of HDC a upstream Sp1 binding in the of Sp1 site the promoter activity was not that through upstream Sp1 site plays a by KLF4 through the downstream a of the GC box in the HDC promoter and the GC by KLF4 a Sp1 and KLF4 in regulation of gene or in KLF4 that the not that KLF4 was binding to or that an mechanism was of KLF4 of transcription from a promoter a binding site not the In to the HDC gastrin also several as M. Raychowdhury R. T. Wiedenmann B. Rosewicz S. Wang T.C. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar), M. N. E. R. E. T. Hocker M. 2001; PubMed Scopus Google Scholar), and factor N.F. Ai W. Raychowdhury R. M. Wang T.C. Koh T.J. McLaughlin J.T. Am. J. Physiol. 2004; Scholar). it has been shown that gastrin the through Sp1 binding in the of factor Sp1 is not involved in gastrin In the human HDC the gastrin responsive elements mapped downstream of the transcriptional initiation site R. Zhang Z. Hocker M. Wang T.C. J. Biol. Chem. 1999; 274: 20961-20969Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar), and the Sp1 binding GC box is located In the current study, we showed that the upstream Sp1 site is the HDC promoter is up-regulated by gastrin further that gastrin gene expression through GC-rich the In addition, the to gastrin KLF4 binding gastrin and KLF4 mapped to the region of the is different and that the not of nuclear factors that bind to three gastrin responsive elements in the HDC promoter and gastrin to the We Sp1 and We also Raychowdhury with and Fleming