Identification of SWI·SNF Complex Subunit BAF60a as a Determinant of the Transactivation Potential of Fos/Jun Dimers

Fos family proteins form stable heterodimers with Jun family proteins, and each heterodimer shows distinctive transactivating potential for regulating cellular growth, differentiation, and development via AP-1 binding sites. However, the molecular mechanism underlying dimer specificity and the molecules that facilitate transactivation remain undefined. Here, we show that BAF60a, a subunit of the SWI·SNF chromatin remodeling complex, is a determinant of the transactivation potential of Fos/Jun dimers. BAF60a binds to a specific subset of Fos/Jun heterodimers using two different interfaces for c-Fos and c-Jun, respectively. Only when the functional SWI·SNF complex is present, can c-Fos/c-Jun (high affinity to BAF60a) but not Fra-2/JunD (no affinity to BAF60a) induce the endogenous AP-1-regulated genes such as collagenase and c-met. These results indicate that a specific subset of Fos/Jun dimers recruits SWI·SNF complex via BAF60a to initiate transcription. Fos family proteins form stable heterodimers with Jun family proteins, and each heterodimer shows distinctive transactivating potential for regulating cellular growth, differentiation, and development via AP-1 binding sites. However, the molecular mechanism underlying dimer specificity and the molecules that facilitate transactivation remain undefined. Here, we show that BAF60a, a subunit of the SWI·SNF chromatin remodeling complex, is a determinant of the transactivation potential of Fos/Jun dimers. BAF60a binds to a specific subset of Fos/Jun heterodimers using two different interfaces for c-Fos and c-Jun, respectively. Only when the functional SWI·SNF complex is present, can c-Fos/c-Jun (high affinity to BAF60a) but not Fra-2/JunD (no affinity to BAF60a) induce the endogenous AP-1-regulated genes such as collagenase and c-met. These results indicate that a specific subset of Fos/Jun dimers recruits SWI·SNF complex via BAF60a to initiate transcription. polymerase chain reaction reverse transcription-PCR gluthathione glutathione S-transferase chloramphenicol acetyltransferase glyceraldehyde-3-phosphate dehydrogenase glucocorticoid receptor Transcription factor AP-1, which plays pivotal roles in cell growth, differentiation, development, and tumor formation, is composed of Fos family proteins (Fos; c-Fos, Fra-1, Fra-2, and FosB) and Jun family proteins (Jun; c-Jun, JunB, and JunD). The members of both families form dimers through a leucine zipper structure; Jun family members can form low-affinity homodimers and high affinity heterodimers with the Fos family (1Curran T. Franza B.R. Cell. 1988; 5: 395-397Abstract Full Text PDF Scopus (1311) Google Scholar, 2Nakabeppu Y. Ryder K. Nathans D. Cell. 1988; 55: 907-915Abstract Full Text PDF PubMed Scopus (531) Google Scholar). However, members of the Fos family do not form stable homodimers. Although these hetero- and homodimers bind to similar sites on DNA (TGAC/GTCA, AP-1 binding sites) through the basic domains of both proteins, each dimer has a distinct transcriptional regulatory function that can be modulated either positively or negatively (3Suzuki T. Okuno H. Yoshida T. Endo T. Nishina H. Iba H. Nucleic Acids Res. 1991; 19: 5537-5542Crossref PubMed Scopus (194) Google Scholar). For example, transcriptional activity of the c-Fos/c-Jun dimer is much higher than the Fra-2/c-Jun dimer. Although functional interactions between some members of the Fos/Jun family of proteins and adaptor proteins such as CREB-binding protein (CBP) or TATA-binding protein (TBP) have been reported (4Bannister A.J. Oehler T. Wilhelm D. Angel P. Kouzarides T. Oncogene. 1995; 11: 2509-2514PubMed Google Scholar, 5Kamei Y. Xu L. Heinzel T. Torchia J. Kuroiuwa R. Gloss B. Lin S.C. Heyman R.A. Rose D.W. Glass C.K. Rosenfeld M.G. Cell. 1996; 85: 403-414Abstract Full Text Full Text PDF PubMed Scopus (1926) Google Scholar), crucial proteins that recognize the dimer specificity and/or facilitate the induction of transcriptional initiation were largely unknown. Therefore, we proposed here to isolate such a crucial protein using a yeast two-hybrid system and have demonstrated that BAF60a (6Wang W. Xue Y. Zhou S. Kuo A. Cairns B.R. Crabtree G.R. Genes Dev. 1996; 10: 2117-2130Crossref PubMed Scopus (570) Google Scholar), a component of the SWI·SNF chromatin remodeling complex, can select specific Fos/Jun dimers and function as a determinant of transcriptional activation via AP-1 binding sites. The Gal4DBD-c-Jun () fusion construct (pDBLeu-cJ(25–187)) was generated by inserting the 0.49 kilobase pair EheI fragment of the rat c-jun gene into the MscI restriction endonuclease cleavage site within the open reading frame of Gal4DBD. For the construction of template DNA for in vitro translation, we first generated a starter plasmid from pGEM2–475/Jun-D, the translation initiation site of which has a Kozak consensus sequence with a unique NcoI site that is preceded by a fragment 475 sequence for an efficient translational initiation (2Nakabeppu Y. Ryder K. Nathans D. Cell. 1988; 55: 907-915Abstract Full Text PDF PubMed Scopus (531) Google Scholar). The 1.0-kilobase pair NcoI-BamHI fragment of pGEM2–475/Jun-D encoding JunD was excised and substituted with a synthetic DNA fragment carrying multiple cloning sites to generate pGEM2–475/Met. A series of c-jun or c-fosdeletions was inserted in-frame into pGEM2-475/Met. Full-length BAF60a cDNA was constructed by inserting a PCR1-generated DNA fragment encoding the N-terminal region into the original partial BAF60a clone, which encodes BAF60a, amino acids 139–475, and was isolated by yeast two-hybrid screening. Glutathione S-transferase (GST)-BAF60a was constructed by inserting the full-length DNA into the pGEX4T vector (Amersham Pharmacia Biotech). For the construction of a retrovirus vector expressing HA-tagged proteins, a synthetic oligo DNA fragment coding the HA sequence was inserted into the unique BamHI site of pBabe-IRES puro (7Ui M. Mizutani T. Takada M. Arai T. Ito T. Murakami M. Koike C. Watanabe T. Yoshimatsu K. Iba H. Biochem. Biophys. Res. Commun. 2000; 278: 97-105Crossref PubMed Scopus (16) Google Scholar) to generate pBabeHA-IRES puro. The DNA fragment was generated by annealing the following two nucleotides: 5′-gatcctaccatgtatccatatgatgttccagattatgctagcctcgcctcgagtggccgacaagcgtctcgcgacggtataccgtgagtaagtagg-3′ and 5′-gatccctacttactcacggtataccgtcgcgagacgcttgtcggccactcgaggcgaggctagcataatctggaacatcatatggatacatggtag-3′. The yeast strain MaV203 (MATα, leu2–3Δ112, trp1–901,his3Δ200, ade2–101, gal4Δ,gal80Δ, SPAL10:: URA3,GAL1::lacZ, HIS3uasGAL1::HISemail protectedLys2,can1R, cyh2R) harboring pDBLeu-cJ () (Fig. 1 A) was transformed by the lithium acetate method with a mouse brain cDNA fusion library inserted into the activation domain vector, pPC86 (Life Technologies, Inc.). Transformants were selected with a HIS3 reporter containing the Gal4 DNA binding sites by seeding onto SC/−Leu/−Trp/−His/+3AT (50 mm) plates. After incubation for 60 h at 30 °C, the plates were replica-cleaned for the reduction of false-positive clones according to the manufacturer's protocol and further incubated at 30 °C for 44 h. The positive clones were confirmed by another promoter system that induces β-galactosidase expression through the same DNA binding domain. β-Galactosidase activity in yeast was assayed according to the manufacturer' s protocol. Virus-packaging cell line BOSC23 and the adenocarcinoma cell line SW13 were grown in Dulbecco's modified Eagle's medium supplemented with 10% fetal calf serum. NIH3T3 cells were grown in Dulbecco's modified Eagle's medium supplemented with 10% calf serum. BOSC23 cells were transfected with pBabeHA-BAF60a-IRES puro, and NIH3T3 cells were infected with the resulting ecotropic retrovirus as described previously (8Ito T. Kabuyama Y. Okazaki S. Kameda T. Murakami M. Iba H. Nucleic Acids Res. 1998; 26: 4868-4873Crossref PubMed Scopus (2) Google Scholar). The GST pull-down assay, SDS-polyacrylamide gel electrophoresis, immunoprecipitation, and Western blotting were performed as described previously (9Murakami M. Sonobe M.H. Ui M. Kabuyama Y. Watanabe H. Wada T. Handa H. Iba H. Oncogene. 1997; 14: 2435-2444Crossref PubMed Scopus (55) Google Scholar) using anti-Brm (Transduction Laboratories, Lexington, KY), anti-HA (Santa Cruz Laboratories, Santa Cruz, CA), anti-c-Jun (Santa Cruz), anti-c-Fos (Oncogene Science, San Diego, CA), and anti-INI1 (Santa Cruz) antibodies. A gel shift assay was performed as described previously (3Suzuki T. Okuno H. Yoshida T. Endo T. Nishina H. Iba H. Nucleic Acids Res. 1991; 19: 5537-5542Crossref PubMed Scopus (194) Google Scholar). Total RNA was prepared from SW13 cells transfected with expression plasmids using an Isogen RNA isolation reagent (Wako) and reverse-transcribed for 30 min at 50 °C. Each PCR regime involved an initial denaturation step at 94 °C, 3 min followed by 30 cycles (for collagenase and c-met) and 25 cycles (for GAPDH) at 94 °C for 30 s, 56 °C for 1 min, and 72 °C for 1 min. RT-PCR was performed within the linear range with Superscript one-step RT-PCR with PlatinumTaq kit (Life Technologies, Inc.). The primer sets and amplified fragment size for RT-PCR were as follows: collagenase, 570 base pairs; forward 5′-atcttttgtcaggggagatcatcg-3′, reverse 5′-acagcccagtacttattccctttg-3′, c-met, 701 base pairs; forward 5′-atgagcactgctttaataggacac-3′, reverse 5′-accaactgtgcatttcaatgtattc-3′, GAPDH, 431 base pairs; forward 5′-tcattgacctcaactacatggtttac-3′, reverse 5′-ggcatggactgtggtcatgagtc-3′. To identify the molecules involved in the transactivation of AP-1, we first proposed to isolate proteins that specifically bind with rat c-Jun N-terminal amino acids 25–187 (Fig.1 A), which reportedly contain transactivation domains (10Alani R. Binetruy B. Dosaka H. Rosenberg R.K. Angle P. Karin M. Birrer M.J. Mol. Cell Biol. 1991; 11: 6286-6295Crossref PubMed Scopus (125) Google Scholar). Using the yeast two-hybrid system, 23 positive clones were obtained upon screening 5 × 105clones of a mouse brain cDNA library. DNA sequence analysis revealed a single cDNA clone encoding the C-terminal half of mouse BAF60a, which is a subunit of the mouse SWI·SNF complex. The SWI·SNF complex is a 2-MDa, multi-subunit, DNA-dependent ATPase that is thought to disrupt repressive chromatin structure (11Peterson C.L. Workman J.L. Curr. Opin. Genet. Dev. 2000; 10: 187-192Crossref PubMed Scopus (381) Google Scholar). Because interaction of c-Jun with the SWI·SNF complex seemed likely to be important for regulation of transcription in vivo, we isolated a cDNA containing the entire open reading frame of BAF60a, which had the same nucleotide sequence as a clone reported previously (6Wang W. Xue Y. Zhou S. Kuo A. Cairns B.R. Crabtree G.R. Genes Dev. 1996; 10: 2117-2130Crossref PubMed Scopus (570) Google Scholar). Escherichia coli-produced, histidine-tagged c-Jun amino acids 1–225 (9Murakami M. Sonobe M.H. Ui M. Kabuyama Y. Watanabe H. Wada T. Handa H. Iba H. Oncogene. 1997; 14: 2435-2444Crossref PubMed Scopus (55) Google Scholar) bound with GST-BAF60a fusion protein but not with GST (data not shown), demonstrating that BAF60a interacts directly with c-Jun. By synthesizing truncation mutants of c-Jun in reticulocyte lysates, we showed that N-terminal amino acids 25–187 of c-Jun were sufficient for binding, but further truncation at either the N-terminal or C-terminal regions totally abolished binding (Fig.1 A). To examine whether BAF60a binds with other members of the Jun family, JunB and JunD proteins were synthesized in reticulocyte lysates and assayed for binding with a recombinant GST-BAF60a fusion protein. In comparison with BAF60a binding with c-Jun, BAF60a displayed weaker binding with JunB and no binding with JunD (Fig. 1 C). This result was somewhat surprising because the BAF60a binding domain of c-Jun includes regions conserved in both JunB and JunD (conserved regions 1–3; Fig. 1 A). Even more surprising was the finding that GST-BAF60a fusion protein bound with in vitrotranslated, full-length c-Fos (Fig. 1 D); c-Fos and c-Jun share little sequence similarity outside of their leucine zipper domains. Among the Fos family proteins, this binding is specific for c-Fos (Fig. 1 D). Analysis of c-Fos truncation mutants indicated that C-terminal amino acids 237–380 are sufficient for BAF60a binding (Fig. 1 B). Binding of BAF60a with v-Fos, which is derived from FBJ-MuSV (12Curran T. Teich N. J. Virol. 1982; 42: 114-122Crossref PubMed Google Scholar), was not detected (Fig.1 B). The C-terminal amino acids of v-Fos and c-Fos are divergent because of a frameshift mutation starting at c-Fos amino acid 333 (13Curran T. Miller A.D. Zokas L. Verma I.M. Cell. 1984; 36: 259-268Abstract Full Text PDF PubMed Scopus (347) Google Scholar) (Fig. 1 B). Therefore, c-Fos C-terminal amino acids 333–380 are likely to be critical for binding with BAF60a. Fos/Jun heterodimers composed of c-Fos and c-Jun, c-Fos and JunD, Fra-2 and c-Jun, or Fra-2 and JunD were assayed for binding with GST-BAF60a by precipitation with glutathione (GSH)-Sepharose beads. GST-BAF60a precipitated 4% of c-Fos alone. Precipitation of c-Fos with BAF60a increased to 7.5% of the total c-Fos when preincubated with an equimolar amount of c-Jun (Fig.2 A), Because the molar amount of c-Jun recovered in the precipitate was nearly equal to the amount of c-Fos, it seems that binding of BAF60a with the c-Fos/c-Jun heterodimer would be preferential to binding with c-Fos alone. Fra-2 alone, JunD alone, and the Fra-2/JunD heterodimer displayed only marginal binding with BAF60a (Fig. 2 D). JunD alone displayed marginal binding with GST-BAF60a, whereas precipitation of the c-Fos/JunD heterodimer with GST-BAF60a resulted in the recovery of 1.5% of the total JunD added to the reaction mixture. These results suggest that BAF60a can simultaneously bind restricted members of Fos family proteins (c-Fos alone) and Jun family proteins (c-Jun, and probably to a lesser extent JunB but not JunD) using different interfaces present in the BAF60a molecule. These results also suggest that the Fos/Jun dimer formation via the leucine zipper region is compatible with formation of a ternary complex composed of Fos, Jun, and BAF60a. A c-Fos/JunD heterodimer bound with GST-BAF60a, but the binding was less than that observed with c-Fos alone (Fig.2 B), suggesting that dimerization of c-Fos and JunD did not to BAF60a dimerization of Fra-2 and c-Jun did not to to BAF60a binding (Fig.2 C). The binding affinity of each heterodimer here positively with their transactivating activity when in cells by expression with a reporter gene containing a single AP-1 binding site derived from the collagenase gene c-Fos/c-Jun had the transactivating and other dimers of either c-Fos or c-Jun had that c-Fos c-Jun had only marginal potential of each Fos/Jun dimer in cells by cells were transfected with expression encoding a of the family and a of the family with activity was to that in cells transfected with the vector and Res. in a cells were transfected with expression encoding a of the family and a of the family with activity was to that in cells transfected with the vector and Res. To examine whether BAF60a the specific DNA binding activity of c-Fos/c-Jun shift were performed with containing the AP-1 DNA binding site of the collagenase shift was not upon of GST alone, but a of the was detected upon the of GST-BAF60a A). These results indicate that BAF60a the specific DNA binding activity of the c-Fos/c-Jun the Fra-2/JunD dimer was the of GST-BAF60a only a of the (data not To whether c-Fos/c-Jun dimer with BAF60a in vivo, NIH3T3 cells expressing HA-tagged BAF60a were to induce c-Fos and c-Jun. Cell lysates were with a bound with histidine-tagged c-Jun. that bound with were recovered and by Western not only HA-tagged BAF60a but also J.L. S. K. J. M. Crabtree G.R. Cell. Full Text PDF PubMed Scopus Google Scholar), the subunit of the SWI·SNF complex (Fig. 3 B). cell lysates of NIH3T3 cells were precipitated with anti-c-Jun and by Western the and SWI·SNF complex subunit (Fig. 3 J.L. S. K. J. M. Crabtree G.R. Cell. Full Text PDF PubMed Scopus Google Scholar). proteins when the anti-c-Jun was by the results were obtained when were performed with anti-c-Fos or proteins were detected when were performed in which no Fos protein (Fig. 3 C). it was that c-Fos and c-Jun with the SWI·SNF complex through BAF60a in These results indicate that BAF60a has a protein for c-Fos, c-Jun, and the other SWI·SNF complex analysis (Fig. of GST-BAF60a revealed the of a domain amino acids which is for binding with either c-Fos or c-Jun synthesized in reticulocyte we domains within the structure of BAF60a that bind with other SWI·SNF complex GST-BAF60a truncation mutants were with cellular lysates prepared from NIH3T3 precipitated with and by Western blotting with anti-Brm was precipitated with the full-length BAF60a. the same domain of BAF60a that binds with c-Fos or c-Jun also binds with the other of the SWI·SNF complex. that these amino acids form a structure and that truncation of this region the structure of the which to a of binding with the c-Fos, c-Jun, and SWI·SNF that directly with BAF60a. whether the transactivating activity of the dimer that binds BAF60a with the is modulated by the functional SWI·SNF complex in were performed with adenocarcinoma cell line SW13 because it of and J.L. S. K. J. M. Crabtree G.R. Cell. Full Text PDF PubMed Scopus Google Scholar), which are critical of the SWI·SNF complex. In each SWI·SNF complex either or but not both (6Wang W. Xue Y. Zhou S. Kuo A. Cairns B.R. Crabtree G.R. Genes Dev. 1996; 10: 2117-2130Crossref PubMed Scopus (570) Google Scholar). Therefore, the of or into SW13 would the formation of functional SWI·SNF complex. of an expression plasmid encoding either c-Fos, or into SW13 cells did not a reporter gene to the AP-1 binding site of the collagenase gene promoter A). of c-jun alone or the activity transactivation by c-Fos/c-Jun was by the of However, by was These results suggest in transactivation by the c-Fos/c-Jun dimer is upon the of the SWI·SNF complex containing protein. the transactivating potential of which binds with marginal affinity to BAF60a, with that of of Fra-2 alone, JunD alone, or into SW13 cells did not the the activity observed in SW13 cells expressing Fra-2 and JunD was not by the of either or (Fig. 5 A). These results suggest that a of the transactivating potential of each Fos/Jun dimer is by binding affinity to BAF60a protein. this the Fos/Jun dimer not to SWI·SNF complex to the AP-1 binding sites. However, the c-Fos/c-Jun dimer some transactivating potential in SW13 cells that functional SWI·SNF complex (Fig. 5 A). Therefore, be some other molecular mechanism that transactivation by the c-Fos/c-Jun dimer. the between in plasmids and in we the of endogenous collagenase A. B. J. PubMed Scopus Google Scholar) and D.W. R. Oncogene. 2000; 19: PubMed Scopus Google Scholar) which were to be through AP-1 binding sites in cells from Total RNA was isolated from SW13 cells transfected with the same of expression but not with the reporter Although each RNA similar amount of as by RT-PCR indicated that the collagenase gene was on of expression for c-Fos, c-Jun, and (Fig. 5 B). These results indicate that the results of is efficient for the induction of collagenase gene for the induction is upon the expression of c-Fos, c-Jun, and (Fig. 5 B). has only marginal on transactivation of this suggesting that the or subunit has distinct specificity to facilitate gene or transactivation was detected when were transfected of and c-jun (Fig. 5 B). demonstrated here that SWI·SNF complex subunit BAF60a binds with distinct to different Fos/Jun dimers by with the N-terminal region of c-Jun and the C-terminal region of c-Fos (Fig. BAF60a binds the c-Fos/c-Jun dimer with the affinity and the other dimers containing either c-Fos or c-Jun with Fos/Jun dimers that contain c-Fos c-Jun have no binding activity (Fig. The binding affinity of each Fos/Jun heterodimer to BAF60a is with the transactivating activity as by expression of each heterodimer in cells These indicate that the SWI·SNF complex is a determinant of transactivation potential of Fos/Jun dimers. in SW13 which functional SWI·SNF complex, the transactivating activity of Fos/Jun dimers is at However, transactivation by c-Fos/c-Jun heterodimer but not by Fra-2/JunD was by or into SW13 to the functional SWI·SNF complex Although we did not the function of BAF60a NIH3T3 cells expressing at high by retrovirus showed no on cellular These cells did not at that a high expression of BAF60a is not sufficient to induce cellular in NIH3T3 cells (data not Although functional have been for the yeast or SWI·SNF complex (11Peterson C.L. Workman J.L. Curr. Opin. Genet. Dev. 2000; 10: 187-192Crossref PubMed Scopus (381) Google Scholar), on AP-1 and on glucocorticoid receptor H. M. A. H. Nucleic Acids Res. PubMed Scopus Google Scholar, B.R. Genes Dev. 1996; 10: PubMed Scopus Google Scholar, 1998; PubMed Scopus Google Scholar), J. Genet. PubMed Scopus Google Scholar), K. Zhou H. Mol. Cell. Full Text Full Text PDF PubMed Scopus Google Cairns B.R. Workman J.L. Mol. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar), and A. Mol. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar) a in which transcription the SWI·SNF complex to genes N. C. S. C.L. Genes Dev. PubMed Scopus Google Scholar). In these with with and or with but not BAF60a were as the SWI·SNF complex that bind directly to transcription These results indicate that the 2-MDa, SWI·SNF complex has different interfaces that with transcription and function as a transcriptional Because the transactivating function of in yeast is to B.R. Genes Dev. 1996; 10: PubMed Scopus Google Scholar), the yeast of BAF60a, we can that AP-1 and for of the of the of SWI·SNF complex present in the cell T. 2000; 26: PubMed Scopus Google Scholar) for their transactivating Therefore, between AP-1 and glucocorticoid receptor transcription for SWI·SNF complex would in the molecular for the of transcription observed between these two C. S. H. P. Cell. Full Text PDF PubMed Scopus Google Scholar, R. P. S. J. N. Verma I.M. Cell. Full Text PDF PubMed Scopus Google Scholar, T. Iba H. Res. 1998; Google Scholar). is that c-Fos and c-Jun are specifically by BAF60a Fos family proteins and Jun family proteins, respectively. and isolated as cellular of by RNA tumor (12Curran T. Teich N. J. Virol. 1982; 42: 114-122Crossref PubMed Google Scholar) and Y. C. M. S. A. PubMed Scopus Google Scholar), and their are to be the the family of Because to a lesser c-jun are the c-Fos/c-Jun dimer would be and would to with the AP-1 binding site H. H. T. M. Iba H. S. A. PubMed Scopus Google D. M. Oncogene. 1997; 14: PubMed Scopus Google Scholar). the chromatin structure would be in an for transactivation of AP-1-regulated affinity binding of c-Fos/c-Jun with BAF60a recruits SWI·SNF complex and induces remodeling of the transcriptional and proteins such as and (4Bannister A.J. Oehler T. Wilhelm D. Angel P. Kouzarides T. Oncogene. 1995; 11: 2509-2514PubMed Google Scholar, 5Kamei Y. Xu L. Heinzel T. Torchia J. Kuroiuwa R. Gloss B. Lin S.C. Heyman R.A. Rose D.W. Glass C.K. Rosenfeld M.G. Cell. 1996; 85: 403-414Abstract Full Text Full Text PDF PubMed Scopus (1926) Google Scholar) are for the initiation of transcription. Because the of the in some has been to of the SWI·SNF complex J. C.L. Workman J.L. S. A. 1998; PubMed Scopus Google Scholar), it is that the within the modified chromatin remain to regulation by other Fos/Jun dimers that are in these dimers SWI·SNF complex. In the between Fos/Jun transcription and chromatin remodeling here is for the underlying that the of AP-1 transcription factor in growth, differentiation, development, and tumor H. for cDNA clones of and and Y. for SW13 also M. (Life Technologies, for on the yeast two-hybrid system T. Kameda for critical reading of the and Y. for of the