Bcl-xL Expression Correlates with Primary Macrophage Differentiation, Activation of Functional Competence, and Survival and Results from Synergistic Transcriptional Activation by Ets2 and PU.1

Abstract

Depriving primary bone marrow-derived macrophages of colony-stimulating factor-1 (CSF-1) induces programmed cell death by apoptosis. We show that cell death is accompanied by decreases in the expression of anti-apoptotic Bcl-xL protein and the Ets2 and PU.1 proteins of the Ets transcription factor family. Macrophages require both priming and triggering signals independent of CSF-1 to kill neoplastic cells or microorganisms, and this activation of macrophage competence is accompanied by increased expression ofbcl-xL, ets2, andPU.1. Furthermore, we show that only Ets2 and PU.1, but not Ets1, function in a synergistic manner to transactivate thebcl-x promoter. The synergy observed between PU.1 and Ets2 is dependent on the transactivation domains of both proteins. Although other transcription factors like Fos, c-Jun, Myc, STAT3, and STAT5a are implicated in the activation of macrophage competence or in CSF-1 signaling, no synergy was observed between Ets2 and these transcription factors on the bcl-x promoter. We demonstrate that the exogenous expression of both Ets2 and PU.1 in macrophages increases the number of viable cells upon CSF-1 depletion and that Ets2 and PU.1 can functionally replace Bcl-xL in inhibiting Bax-induced apoptosis. Together, these results demonstrate that PU.1 and Ets2 dramatically increase bcl-x activation, which is necessary for the cytocidal function and survival of macrophages. Depriving primary bone marrow-derived macrophages of colony-stimulating factor-1 (CSF-1) induces programmed cell death by apoptosis. We show that cell death is accompanied by decreases in the expression of anti-apoptotic Bcl-xL protein and the Ets2 and PU.1 proteins of the Ets transcription factor family. Macrophages require both priming and triggering signals independent of CSF-1 to kill neoplastic cells or microorganisms, and this activation of macrophage competence is accompanied by increased expression ofbcl-xL, ets2, andPU.1. Furthermore, we show that only Ets2 and PU.1, but not Ets1, function in a synergistic manner to transactivate thebcl-x promoter. The synergy observed between PU.1 and Ets2 is dependent on the transactivation domains of both proteins. Although other transcription factors like Fos, c-Jun, Myc, STAT3, and STAT5a are implicated in the activation of macrophage competence or in CSF-1 signaling, no synergy was observed between Ets2 and these transcription factors on the bcl-x promoter. We demonstrate that the exogenous expression of both Ets2 and PU.1 in macrophages increases the number of viable cells upon CSF-1 depletion and that Ets2 and PU.1 can functionally replace Bcl-xL in inhibiting Bax-induced apoptosis. Together, these results demonstrate that PU.1 and Ets2 dramatically increase bcl-x activation, which is necessary for the cytocidal function and survival of macrophages. colony-stimulating factor-1 colony-stimulating factor-1 receptor phosphate-buffered saline interferon-γ lipopolysaccharide hemagglutinin signal transducer and activator of transcription mitogen-activated protein kinase fluorescence-activated cell sorting bone-derived macrophages upstream stimulatory factor-1 Fos-interacting protein interferon-α activation sequence Ets-binding sites The Ets family of transcription factors consists of ∼30 members conserved from sea urchins to man. Ets members contain a conserved DNA-binding domain of ∼85 amino acids known as the Ets domain (reviewed in Ref. 1Ghysdael J. Boureux A. Yaniv M. Ghysdael J. Oncogenes as Transcriptional Regulators: Retroviral Oncogenes. 1. Birkhaeuser Verlag, Basel, Switzerland1997: 29-88Crossref Google Scholar). Ets1, the progenitor of v-Ets found in the E26 retrovirus, and Ets2 are 97% conserved in the Ets domain, whereas PU.1/Spi.1 is highly divergent in this domain (37% identity) (2Wasylyk B. Hahn S.L. Giovane A. Eur. J. Biochem. 1993; 211: 7-18Crossref PubMed Scopus (811) Google Scholar). These differences in sequence identity of the Ets domain allow Ets1, Ets2, and PU.1 to bind to common as well as distinct optimal DNA target sequences. Ets proteins bind to DNA as monomers to activate transcription alone or in conjunction with other transcription factors binding to their respective sites (reviewed in Ref. 1Ghysdael J. Boureux A. Yaniv M. Ghysdael J. Oncogenes as Transcriptional Regulators: Retroviral Oncogenes. 1. Birkhaeuser Verlag, Basel, Switzerland1997: 29-88Crossref Google Scholar). PU.1 is expressed in early progenitor cells as well as in fully differentiated B cells, neutrophils, and macrophages. The importance of PU.1 in hematopoietic development has been confirmed by PU.1gene disruption studies showing that PU.1-deficient mice lack mature B cells, neutrophils, and macrophages (3McKercher S. Torbett B. Anderson K. Henkel G. Vestal D. Baribault H. Klemsz M. Feeney A. Wu G. Paige C. Maki R. EMBO J. 1996; 15: 5647-5658Crossref PubMed Scopus (929) Google Scholar, 4Scott E.W. Simon M.C. Anastasi J. Singh H. Science. 1994; 265: 1573-1577Crossref PubMed Scopus (1279) Google Scholar).ets2 null mice die early during embryonic development (5Yamamoto H. Flannery M.L. Kupriyanov S. Pearce J. McKercher S.R. Henkel G.W. Maki R.A. Werb Z. Oshima R.G. Genes Dev. 1998; 12: 1315-1326Crossref PubMed Scopus (255) Google Scholar). However, transgenic studies using a dominant-negative form of Ets2 under the control of a monocyte/macrophage-specific promoter have provided insight into the role of Ets2 in macrophages (6Jin D.I. Jameson S.B. Reddy M.A. Schenkman D. Ostrowski M.C. Mol. Cell. Biol. 1995; 15: 693-703Crossref PubMed Google Scholar). Abnormal macrophage development occurs in these transgenic mice during the first 40 days following birth, and peritoneal macrophages obtained from these transgenic animals do not have the characteristic macrophage morphology when cultivated in vitro with CSF-1.1 These results imply the importance of Ets2 in the development of macrophages, yet the molecular mechanisms by which Ets2 functions had not been elucidated in these studies. The level of PU.1 is highly abundant in immature myeloid progenitor cells, and this level of expression remains high throughout macrophage differentiation (7Aperlo C. Pognonec P. Stanley E.R. Boulukos K.E. Mol. Cell. Biol. 1996; 16: 6851-6858Crossref PubMed Scopus (37) Google Scholar, 8Stacey K. Fowles L. Colman M. Ostrowski M. Hume D. Mol. Cell. Biol. 1995; 15: 3430-3441Crossref PubMed Scopus (129) Google Scholar). In contrast, Ets2 is not expressed in early myeloid progenitors, but later in more mature myeloid cells (9Boulukos K.E. Pognonec P. Begue A. Gesquière J.C. Stéhelin D. Ghysdael J. EMBO J. 1988; 7: 697-705Crossref PubMed Scopus (77) Google Scholar, 10Boulukos K.E. Pognonec P. Sariban E. Bailly M. Lagrou C. Ghysdael J. Genes Dev. 1990; 4: 401-409Crossref PubMed Scopus (40) Google Scholar, 11Ghysdael J. Gegonne A. Pognonec P. Boulukos K. Leprince D. Dernis D. Lagrou C. Stéhelin D. EMBO J. 1986; 5: 2251-2256Crossref PubMed Scopus (9) Google Scholar), and Ets2 become rapidly up-regulated upon induction of macrophage differentiation or activation of primary macrophages (10Boulukos K.E. Pognonec P. Sariban E. Bailly M. Lagrou C. Ghysdael J. Genes Dev. 1990; 4: 401-409Crossref PubMed Scopus (40) Google Scholar). Bcl-xL is believed to be the key anti-apoptotic protein expressed in myeloid precursors and macrophages (12Chatterjee D. Han Z. Mendoza J. Goodglick L. Hendrickson E.A. Pantazis P. Wyche J.H. Cell Growth Differ. 1997; 8: 1083-1089PubMed Google Scholar, 13Lotem J. Sachs L. Cell Growth Differ. 1995; 6: 647-653PubMed Google Scholar, 14Okada S. Zhang H. Hatano M. Tokuhisa T. J. Immunol. 1998; 160: 2590-2596PubMed Google Scholar, 15Packham G. White E.L. Eischen C.M. Yang H. Parganas E. Ihle J.N. Grillot D.A.M. Zambetti G.P. Nunez G. Cleveland J.L. Genes Dev. 1998; 12: 2475-2487Crossref PubMed Scopus (100) Google Scholar, 16Sanz C. Benito A. Silva M. Albella B. Richard C. Segovia J.C. Insunza A. Bueren J.A. Fernandez-Luna J.L. Blood. 1997; 89: 3199-3204Crossref PubMed Google Scholar, 17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). In contrast, Bcl-2 is down-regulated in these systems. Recently, we showed that the induction of bcl-xL results from an increase inbcl-x promoter activity and that de novo protein synthesis is required for this activation of bcl-xtranscription (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). The human bcl-x promoter contains nine potential EBS. The capacities of PU.1 and Ets2 to transactivate the bcl-x promoter to PU.1 and Ets2 or in synergy to transactivate this promoter. In we to the of the of PU.1, in primary macrophages upon induction of and differentiation and activation of macrophage competence and during programmed cell death by apoptosis. cells, cells, and cells the S. A. PubMed Scopus Google in and bone marrow-derived cells from of with to in cells cultivated in and from cells as a of CSF-1 E.R. or in and of human fully differentiated macrophages CSF-1 was the are or was to macrophages for The and macrophage cell have been (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). macrophages with of and of or with of and of of as (7Aperlo C. Pognonec P. Stanley E.R. Boulukos K.E. Mol. Cell. Biol. 1996; 16: 6851-6858Crossref PubMed Scopus (37) Google Scholar). cells Ets2 with of or the cells with CSF-1 in in and the cells cultivated in and with or as a of The number of viable cells was by The of the of the bcl-x upstream of the has been (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). Ets2, a dominant-negative of Ets2 Ets1, and PU.1/Spi.1 into M. A. T. R. H. Cell. 1990; PubMed Scopus Google to and as (7Aperlo C. Pognonec P. Stanley E.R. Boulukos K.E. Mol. Cell. Biol. 1996; 16: 6851-6858Crossref PubMed Scopus (37) Google Scholar, 17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). hemagglutinin was upstream of the first of Ets2, Ets1, or was by to the transactivation domains found in the first amino was upstream of the cells by the in by cells in to and to of or or of or In these of was as an control for in cells or cells by the or with using of the in the of of or as in the with of as an control for as of the was to protein by and the other was to and in cells or cells the by the or with as for activity was using the was in with of or P. Boulukos K.E. Aperlo C. M. H. A. H. 1997; PubMed Scopus Google and of as (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). activity was using the in the of or STAT5a into and activation of cells with in with of STAT3, and the cells in for with CSF-1 for independent using the cell and DNA in or Cell as C. Boulukos K.E. J. Pognonec P. 1996; PubMed Scopus Google Scholar). cells in and and for and as by the the and on a to as an control for in in as by the of was and on a and to a as by the of T. A. and as with high using the as by the and in a of and using and to with in and of protein from on proteins to a as by the using or of and by as by the macrophage cells with of with on the of cells was as by the with the following cells with and in binding in for in and with a of for in and in and was to the and cells the of or cells the of by to the number of viable The number of cells was with to the number of viable cells in and the following using the with of of DNA as in the of a protein was in cells and with following the The cells on a using the to cells of and the cells found these using the CSF-1 induces primary bone marrow-derived cells to and to into macrophages We C. L. S. Pognonec P. Boulukos K.E. Cell Growth Differ. 1998; Google and Blood. 1996; PubMed Google have that of hematopoietic or cells with factor the We obtained using of CSF-1 and in the of on morphology not and the expression of a with functions obtained with both of CSF-1 However, macrophages obtained with of CSF-1 that PU.1 was expressed under both the expression of M. However, expression was when a high of CSF-1 was is that increases in Ets2 expression are to a induction of expression has been to bone and development in transgenic mice T. C.M. R. A. 1996; PubMed Scopus Google Scholar). expression was was expressed These results show that is a of expression upon of primary cells with of CSF-1 necessary to and In to and CSF-1 is required for the survival of the expression of PU.1, ets2, and bcl-xL upon death or survival we first bone marrow-derived cells with CSF-1 for days to of CSF-1 or with of CSF-1 or for Macrophages and in is the morphology of primary macrophages upon the and a number of cells to cells was observed or of The number of macrophages in the or of of CSF-1 with the number of cells of viable cells confirmed by for demonstrate that the cell death observed in the of CSF-1 was to programmed cell death by macrophages with or of CSF-1 with an early of apoptosis. in in the of of the cells with V. The number of cells with and the of these that the was of primary bone marrow-derived macrophages induces programmed cell death by apoptosis. differentiated primary macrophages with or of CSF-1 for with and as a control for of cells and that the cell death observed in is accompanied by decreases in Bcl-xL protein was using obtained from of CSF-1 for and with of CSF-1 or and the was with an both anti-apoptotic Bcl-xL and proteins. in Bcl-xL in the of with increases in cell The was not in these The of Ets2 and PU.1 proteins with of The from these results is that is a between the of Ets2, PU.1, and Bcl-xL protein expression and was as a control for the of protein on the cytocidal activity for neoplastic cells or both priming and triggering and triggering by and rapidly expression in the of CSF-1 M. P. D. A. Stanley E.R. J. Immunol. Google Scholar, G. J.A. J. Cell PubMed Scopus Google Scholar). In and expression on de novo protein synthesis S. Zhang H. Hatano M. Tokuhisa T. J. Immunol. 1998; 160: 2590-2596PubMed Google Scholar). the of bcl-xL and expression independent of we primary macrophages with and in a with or up-regulated the expression of ets2, andPU.1. was as a control of an or R. S. A. 1993; PubMed Scopus Google Scholar). These results demonstrate that ets2, and PU.1 are in macrophages not only a CSF-1 and survival but upon activation of macrophage functions independent of and results show that PU.1, Ets2, and Bcl-xL are expressed upon CSF-1 or differentiation signals in primary macrophages. In of macrophages with and which CSF-1 M. P. D. A. Stanley E.R. J. Immunol. Google Scholar, G. J.A. J. Cell PubMed Scopus Google Scholar), PU.1, and PU.1 (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google and Ets2 (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar, J. A. M. G. D. Hume D. Ostrowski M. Mol. Cell. Biol. PubMed Scopus Google transactivate the bcl-x and PU.1 and Ets2 when we the bcl-xL we these transcription factors or in bcl-x cells in these studies for is not to primary macrophages to their cell death following of DNA to these cells Hume Immunol. Cell Biol. 1993; PubMed Google Scholar). no Ets2 or PU.1 was by not in cells, potential from expressed proteins. we that Ets1, Ets2, and PU.1 expressed in cells in B are the of the Ets2 and PU.1 proteins following of human In these the of as the of increased to the of Ets proteins Ets transactivation studies from the are using the of the bcl-x upstream of the as the The when both Ets2 and PU.1 expressed of when protein was expressed but the of that this is in other cell using cells results obtained using cells, in which Ets2 and PU.1 the bcl-x promoter Ets2 or PU.1 These under of activation is more when both PU.1 and Ets2 are In other the exogenous of Ets proteins PU.1 and Ets2 transactivate the bcl-x promoter PU.1 or Ets2 alone in cell from in this promoter activity was in to allow for the of a of Ets2 PU.1 the of PU.1 or Ets2 alone an increase in activation was observed the of both PU.1 and Ets2 their capacities to transactivate thebcl-x promoter. The observed with Ets2 and PU.1 from a synergistic not an between these other Ets proteins with PU.1 or Ets2, the following cells with Ets2 and or and PU.1 In the the of DNA alone the bcl-x promoter Ets2 the of or Ets2 the The bcl-x promoter activity was not by with of both and results obtained using and PU.1 with and PU.1 not in a synergistic on the bcl-x promoter. These results that the to transactivate the in a synergistic manner is to the Ets proteins PU.1 and The bcl-x promoter contains binding sites for other transcription an for and an for and and sites for proteins. of macrophage competence is accompanied by increases in and expression Ref. Hume J. Biol. 1996; PubMed Scopus Google Scholar). CSF-1 of the results in the of Fos, and Cleveland J.L. PubMed Scopus Google Scholar), and CSF-1 in and in the cell L. V. A. J.A. Blood. 1995; PubMed Google Scholar), we these transcription factors activate transcription on thebcl-x promoter in with of and to a increase in activity with a increase for was observed following of the bcl-x promoter with Fos, c-Jun, and Ets2 induction of Although and the not no synergy was observed with of these proteins and Ets2 not CSF-1 induces proteins to to the and become transcription factors L. V. A. J.A. Blood. 1995; PubMed Google Scholar). but not not the activation of cells the Cleveland J.L. PubMed Scopus Google with have been obtained upon or of or cells, (reviewed in Ref. L. A. Pognonec P. Boulukos K.E. 16: Google Scholar). when STAT5a and Ets2 the transactivation capacities of Ets2 to be by STAT5a Together, these results that CSF-1 activation of these transcription factors is not necessary for the of transcription of the bcl-x but more for the of other target the transactivation domain or the DNA-binding domain of the Ets2 protein is necessary for this synergistic with PU.1, we PU.1 with to but transactivation domain is In with the results obtained in the transactivation capacities of PU.1 alone increased with of However, these capacities not by of These results show that not with the potential of PU.1 to transactivate the bcl-x but that the transactivation domain of Ets2 is required for synergistic with the transactivation domain of PU.1 was to of with Ets2 that of Ets2 in increased of the bcl-x yet no synergy was observed with these results show that the transactivation domains of both Ets2 and PU.1 are necessary for the synergy observed between these proteins. The demonstrate that the expression of Ets2, PU.1, and Bcl-xL decreases in primary of CSF-1 and that this in expression with the of apoptosis. We showed that Ets2 and PU.1 function in synergy to transactivate the bcl-x yet these do not demonstrate that the between expression of Ets2, PU.1, and Bcl-xL and of is this the following using cell The macrophage cell is dependent on CSF-1 for and CSF-1 depletion of these cells results in of cell death observed with primary macrophages. We a that Ets2 in the of CSF-1 (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). PU.1 and Ets2 in macrophages to by CSF-1 we cells with PU.1 and Ets2 expression In cells with and In a of of cells with a control expression or with cells into and first with CSF-1 to allow cells to to in and in the or of the of viable cells by The first is that cell survival of cells, as well as of the cell on the of of PU.1 and Ets2 results in a increase in cell death to of a control or expression Ets2 and PU.1 proteins increase in cell death is independent of the that Ets2 and PU.1 be in other cell survival in macrophages independent of as with and is that in cells with a control expression or and cell was and in cell was that the of is to macrophages and is not to the of in other cell not The is the cells, to CSF-1 depletion is in the when the form of PU.1 is expressed CSF-1 depletion of cells in more cell death when both PU.1 and Ets2 are expressed these results show that Ets2 and PU.1 in macrophage in both a and studies showed that the expression of the protein in cells induces whereas is when with Bcl-xL in these cells B. A. M. J. S. C. Mol. Cell. Biol. 1999; 19: PubMed Google Scholar). Ets2 and PU.1 activate the transcription of thebcl-x as a the expression of the Bcl-xL we Ets2 and PU.1 functionally replace the exogenous expression of Bcl-xL to Bax-induced apoptosis. cells in the of an protein expression and with an expression as a with with Bcl-xL and or with Ets2, PU.1, and the cells with and by in are the cells with V. In with studies B. A. M. J. S. C. Mol. Cell. Biol. 1999; 19: PubMed Google Scholar), as by the of cells the In contrast, the of cells in with and Bcl-xL was to control The obtained with Ets2, PU.1, and was to that obtained with and In other Ets2 and PU.1 functionally Bcl-xL in these studies. these results demonstrate that both PU.1 and Ets2 function to and do by the expression of the bcl-x which results in the induction of Bcl-xL CSF-1 is necessary for the and differentiation of myeloid In this we show that is a of expression of in macrophages differentiated from primary bone marrow-derived progenitor is is but only when of CSF-1 are to Depriving fully differentiated primary of CSF-1 induces these cells to die by apoptosis. cell death is accompanied by of Ets2, PU.1 and and when primary are and with the expression of both Ets2, PU.1 and Bcl-xL is and are in a CSF-1 The induction of macrophage and by and is independent of CSF-1 M. P. D. A. Stanley E.R. J. Immunol. Google Scholar, G. J.A. J. Cell PubMed Scopus Google Scholar). and Bcl-xL expression in peritoneal macrophages S. Zhang H. Hatano M. Tokuhisa T. J. Immunol. 1998; 160: 2590-2596PubMed Google and increase PU.1 DNA binding in macrophages R. J. Immunol. 1995; Google Scholar). In this we show that and induces and PU.1 in We showed that the bcl-xL has a (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). In this we show that programmed cell death of primary by CSF-1 with Bcl-xL protein expression and is not to the of the factor of primary results from of the bcl-x as by results using differentiated macrophages are in with of G. White E.L. Eischen C.M. Yang H. Parganas E. Ihle J.N. Grillot D.A.M. Zambetti G.P. Nunez G. Cleveland J.L. Genes Dev. 1998; 12: 2475-2487Crossref PubMed Scopus (100) Google Scholar), showed that of primary myeloid cells upon results in bcl-xL and not in of the Bcl-xL Together, these studies demonstrate that Bcl-xL is more but is in myeloid cells independent of their or their cell survival Although the expression of PU.1 is necessary to macrophage differentiation from immature cells, the expression of PU.1 alone is not to the macrophage cell in the of In contrast, Ets2 expression macrophages from cell death by PU.1 (17Sevilla L. Aperlo C. Dulic V. Chambard J.C. Boutonnet C. Pasquier O. Pognonec P. Boulukos K.E. Mol. Cell. Biol. 1999; 19: 2624-2634Crossref PubMed Scopus (91) Google Scholar). The that we in this is are the functions of these members of the Ets family in differentiated macrophages. this we the activity of both factors and on the We showed that both Ets2 and PU.1 to transactivate the bcl-x a synergistic activation was observed when both that a level of PU.1 bcl-x the expression of the highly Ets2 protein results in a increase in bcl-x of Bcl-xL expression cell survival and a of macrophages when both Ets proteins are is to that the synergy between Ets family members PU.1 and Ets2 on the bcl-x promoter is of Ets2 and or of PU.1 and do not in increased is not expressed in macrophages, is highly expressed during of P. Boulukos K.E. Gegonne A. Bailly M. Stéhelin D. Ghysdael J. Scholar, P. Boulukos K.E. Gesquière J.C. Stéhelin D. Ghysdael J. EMBO J. 1988; 7: PubMed Scopus Google when Bcl-xL is not expressed A. J.C. B. E. L. S. A. 1995; PubMed Scopus Google Scholar, G.P. White J. 1995; PubMed Scopus Google Scholar). Together, these that the expression of Ets family members functions on thebcl-x promoter. we showed that both PU.1 and Ets2 transactivation domains are required for this The of the bcl-x promoter is necessary for synergy between Ets2 and PU.1 of or more sites the of these transcription factors to not We observed that other transcription factors like and or not which are up-regulated CSF-1 only transactivate the bcl-x promoter their or with Ets2 in only an in and STAT5a transcription factors become and into the CSF-1 L. V. A. J.A. Blood. 1995; PubMed Google and have been to transactivate the bcl-x promoter (reviewed in L. A. Pognonec P. Boulukos K.E. 16: Google Scholar). STAT5a and Ets2 are that STAT5a Ets2 transactivation be to for sites to of STAT5a or by the of an to with These results the role of Ets2 and PU.1 in bcl-x (6Jin D.I. Jameson S.B. Reddy M.A. Schenkman D. Ostrowski M.C. Mol. Cell. Biol. 1995; 15: 693-703Crossref PubMed Google that primary peritoneal macrophages obtained from transgenic animals die rapidly by upon of but the by which Ets2 functions to cell death was not be by results showing that a in activity be to the lack of synergy between Ets2 and PU.1 the activation of bcl-x we have that expression is by CSF-1 in primary bone marrow-derived cells as to or when differentiated by CSF-1 The induction of bcl-xL is not to CSF-1 priming and triggering signals independent of CSF-1 ets2, PU.1, and We show that expression of both Ets2 and PU.1 in macrophages increases cell We demonstrate that both proteins function to a PU.1 in macrophages Ets2 results in cell we show that Ets2 and PU.1 can functionally replace Bcl-xL in inhibiting by the protein is the first showing that bcl-x members of the transcription factor family and and that these proteins function in synergy to activate the transcription of the bcl-x in the synthesis of the anti-apoptotic Bcl-xL