TAF7 (TAFII55) plays a role in the transcription activation by c-Jun (original) (raw)
Proceedings of the National Academy of Sciences, 1992
Transcription factor c-Jun appears to be a nuclear target of the Ras-induced signal transduction pathway. In fact, some experiments show that transforming forms of the Ras protein cooperate with Jun in transcriptional activation mediated by an AP-1 site and others indicate that the two oncoproteins cooperate in cellular transformation. Although it is likely that intracellular signaling systems activated by Ras might act directly on c-Jun by inducing specific phosphorylation, it is unclear how c-Jun participates in the transformation process. Here, we present results obtained with a LexA-Jun zipper fusion that lacks both the transcriptional activation domains and the basic region of the DNA-binding domain of c-Jun and contains only the intact leucine-zipper domain. This fusion product has a dominant negative effect on the transcriptional activation elicited by phorbol esters, c-Jun, c-Fos, Ras and E1A on an AP-1-responsive site. An analogous LexA-Fos zipper fusion has similar effects...
Biochemical and Biophysical Research Communications, 2010
Leucine zippers, structural motifs typically comprised of five successive heptads of amino acids with a signature leucine at every seventh position, play a central role in the dimerization of bZIP family of transcription factors and their subsequent binding to the DNA promoter regions of target genes. Herein, using analytical laser scattering (ALS) in combination with isothermal titration calorimetry (ITC), we study the effect of successive C-terminal truncation of leucine zippers on the dimerization and energetics of binding of bZIP domains of Jun transcription factor to its DNA response element. Our data show that all five heptads are critical for the dimerization of bZIP domains and that the successive C-terminal truncation of residues leading up to each signature leucine significantly compromises the binding of bZIP domains to DNA. Taken together, our study provides novel insights into the energetic contributions of leucine zippers to the binding of bZIP domains of Jun transcription factor to DNA.
Journal of Biological Chemistry, 2001
Heterodimeric transcription regulatory proteins can bind to palindromic recognition elements in two opposite orientations. We have developed a gel-based fluorescence resonance energy transfer (gelFRET) assay for quantifying heterodimer orientation preferences. Fos-Jun heterodimers bind in opposite orientations to AP-1 sites with different flanking sequences. The effects of individual amino acid and base pair substitutions on heterodimer binding orientation were quantified. Base pairs at positions ±6 and ±10 relative to the center of the AP-1 site were the principal determinants of Fos-Jun binding orientation. Amino acid residues of opposite charge adjacent to the basic regions of Fos and Jun had independent effects on heterodimer orientation. Exchange of these amino acid residues between the bZIP domains of Fos and Jun reversed the binding orientation. Heterodimers formed by full-length Fos and Jun exhibited the same changes in binding orientation in response to amino acid and base pair substitutions. The preferred orientation of heterodimer binding affected the stability of Fos-Jun-NFAT1 complexes at composite regulatory elements. Changes in heterodimer orientation preference altered the transcriptional activity and the promoter selectivity of Fos-Jun-NFAT1 complexes. Consequently, the orientation of Fos-Jun binding can influence transcriptional activity by altering cooperative interactions with other transcription regulatory proteins. by guest on March 13, 2016 http://www.jbc.org/ Downloaded from Ramirez-Carrozzi and Kerppola 3 Regulation of the transcriptional activities of the myriad of genes in mammalian genomes requires combinatorial interactions among multiple transcription regulatory proteins within promoter and enhancer regions (reviewed in 1). Whether the regulation occurs at the level of chromatin remodeling, coactivator recruitment, or assembly of the transcription machinery, specification of a unique target in the genome requires cooperation among multiple transcription factors (2-5). The cooperative interactions among many transcription regulatory proteins require juxtaposition of contact surfaces that are either part of, or tightly coupled to the DNA binding domain (6-9). Interactions among such proteins generally require a specific spacing and orientation of the DNA recognition sequences to allow cooperative complex formation. Many mammalian transcription regulatory proteins form heterodimers that recognize palindromic DNA sequence elements. Such heterodimers can potentially bind to their recognition sequences in either of two opposite orientations. Heterodimers that bind in opposite orientations can differ in their interactions with transcription factors that bind to adjacent regulatory elements. The binding orientations of such heterodimers may be controlled by recognition of asymmetric base pairs flanking the palindromic core sequence element, or through interactions with other transcription factors (8,10-12). Promoter elements are classically defined based on their position-and orientationdependent transcriptional activities. The orientation of heterodimer binding to asymmetric regulatory elements can influence their transcriptional activities (12-15). The mechanisms whereby the orientation of heterodimer binding influences transcriptional activity remain to be characterized. Fos and Jun are members of the bZIP family of transcription factors and bind to palindromic AP-1 regulatory elements. The X-ray crystal structure of the bZIP domains of Fos and Jun bound to the AP-1 site revealed that the heterodimer could bind to the recognition element in both orientations (16). In solution, Fos-Jun heterodimers bind to different AP-1 sites in opposite preferred orientations (11,17,18). The orientation of heterodimer binding is affected by sequences flanking the palindromic by guest on March 13, 2016 http://www.jbc.org/ Downloaded from Ramirez-Carrozzi and Kerppola 4 core AP-1 recognition element and amino acid residues adjacent to the basic regions of Fos and Jun (11). No direct contacts between the amino acid residues adjacent to the basic regions of Fos-Jun and the base pairs flanking the AP-1 site are observed in the X-ray crystal structure (16). Thus, the orientation of Fos-Jun binding appears to be controlled by indirect recognition of differences in DNA structure between flanking sequences on opposite sides of the AP-1 site. Fos and Jun activate different genes in different cell types and in response to different extracellular signals (19). These differences in Fos-Jun regulatory specificity are mediated at least in part by cooperative interactions with structurally unrelated transcription factors. Fos-Jun heterodimers can physically and functionally interact with members of the NFAT, Ets, Smad, and nuclear hormone receptor transcription factor families (9,20,21). The interaction between Fos-Jun and NFAT1 (NFATp, NFATc2) has been characterized in greatest detail. Cooperative binding by Fos-Jun and NFAT1 to composite regulatory elements in cytokine gene promoters requires a specific orientation of Fos-Jun binding (8,10). The X-ray crystal structure of the Fos-Jun-NFAT1 complex at the ARRE2 element shows a specific contact interface between NFAT1 and one face of the leucine zipper (7). The interaction with NFAT1 can reverse the orientation of heterodimer binding (8). However, the preferred orientation of Fos-Jun binding may influence the stability or the transcriptional activity of Fos-Jun-NFAT1 complexes. We have investigated the structural basis and the functional significance of the opposite orientations of Fos-Jun heterodimer binding at different AP-1 sites. To compare the effects of individual base pairs and amino acid residues on heterodimer orientation, we developed an approach for determination of the free energy of Fos-Jun heterodimer reorientation at different AP-1 sites. The functional consequences of opposite orientations of Fos-Jun heterodimer binding were examined by comparing the stabilities and transcriptional activities of Fos-Jun-NFAT1 complexes formed by heterodimers with opposite orientation preferences. by guest on March 13, 2016 http://www.jbc.org/ Downloaded from Ramirez-Carrozzi and Kerppola 5 Experimental Procedures
1989
fra-1 encodes a serum-inducible protein (Fra-1) that is antigenically related to Fos. We have characterized Fra-1 expression in serum-stimulated cells using antibodies raised against several regions of this protein. Fra-1, expressed transiently in COS cells or in serum-stimulated rat fibroblasts, undergoes extensive post-translational modification, primarily by phosphorylation of serine residues. It is present in both the nucleus and the cytoplasm and participates in a protein complex with Jun. Using proteins synthesized in reticulocyte lysates, we have shown that Fra-1, like Fos, binds to the AP-1 recognition element cooperatively with Jun. A truncated Fra-1 protein that contains the leucine zipper region but not an adjacent basic amino acid domain, complexes with Jun in vitro but fails to bind AP-1 oligonucleotides. These results demonstrate that Fra-1 contributes to the DNA-binding activity ascribed to transcription factor AP-1.
A functional interaction between ATF7 and TAF12 that is modulated by TAF4
Oncogene, 2005
The ATF7 proteins, which are members of the cyclic AMP responsive binding protein (CREB)/activating transcription factor (ATF) family of transcription factors, display quite versatile properties: they can interact with the adenovirus E1a oncoprotein, mediating part of its transcriptional activity; they heterodimerize with the Jun, Fos or related transcription factors, likely modulating their DNA-binding specificity; they also recruit to the promoter a stress-induced protein kinase (JNK2). In the present study, we investigate the functional relationships of ATF7 with hsTAF12 (formerly hsTAF II 20/15), which has originally been identified as a component of the general transcription factor TFIID. We show that overexpression of hsTAF12 potentiates ATF7-induced transcriptional activation through direct interaction with ATF7, suggesting that TAF12 is a functional partner of ATF7. In support of this conclusion, chromatin immunoprecipitation experiments confirm the interaction of ATF7 with TAF12 on an ATF7-responsive promoter, in the absence of any artificial overexpression of both proteins. We also show that the TAF12-dependent transcriptional activation is competitively inhibited by TAF4. Although both TAF12 isoforms (TAF12-1 and -2, formerly TAF II 20 and TAF II 15) interact with the ATF7 activation region through their histone-fold domain, only the largest, hsTAF12-1, mediates transcriptional activation through its N-terminal region.
Biopolymers (Peptide Science), 1998
c-Jun is an oncoprotein that comprises a portion of the AP-1 transcription factor and belongs to the basic-leucine zipper (bZIP) DNA binding protein family. Using peptides derived from the leucine zipper region of Fos, we have developed agents that inhibit Jun's DNA binding in the low micromolar range. Fos peptides that were effective inhibitors in the DNA binding assay were also found to inhibit cellular Jun binding to an AP-1 site in a luciferase reporter plasmid in MCF-7 cells. Size exclusion studies confirmed that peptides that inhibit the DNA binding of Jun also inhibit its dimerization. These peptides were found to have a cytotoxic effect on the MCF-7 cell line when delivered with the transfecting agent Tfx-50, possibly due to their role as transcription factor regulators.
Oncogene, 2001
Fos and Jun family proteins regulate the expression of a myriad of genes in a variety of tissues and cell types. This functional versatility emerges from their interactions with related bZIP proteins and with structurally unrelated transcription factors. These interactions at composite regulatory elements produce nucleoprotein complexes with high sequence-speci®city and regulatory selectivity. Several general principles including binding cooperativity and conformational adaptability have emerged from studies of regulatory complexes containing Fos-Jun family proteins. The structural properties of Fos-Jun family proteins including opposite orientations of heterodimer binding and the ability to bend DNA can contribute to the assembly and functions of such complexes. The cooperative recruitment of transcription factors, coactivators and chromatin remodeling factors to promoter and enhancer regions generates multiprotein transcription regulatory complexes with cell-and stimulus-speci®c transcriptional activities. The gene-speci®c architecture of these complexes can mediate the selective control of transcriptional activity. Oncogene (2001) 20, 2438 ± 2452.
The Leucine Zipper Domains of the Transcription Factors GCN4 and c-Jun Have Ribonuclease Activity
PLoS ONE, 2010
Basic-region leucine zipper (bZIP) proteins are one of the largest transcription factor families that regulate a wide range of cellular functions. Owing to the stability of their coiled coil structure leucine zipper (LZ) domains of bZIP factors are widely employed as dimerization motifs in protein engineering studies. In the course of one such study, the X-ray structure of the retro-version of the LZ moiety of yeast transcriptional activator GCN4 suggested that this retro-LZ may have ribonuclease activity. Here we show that not only the retro-LZ but also the authentic LZ of GCN4 has weak but distinct ribonuclease activity. The observed cleavage of RNA is unspecific, it is not suppressed by the ribonuclease A inhibitor RNasin and involves the breakage of 39,59-phosphodiester bonds with formation of 29,39-cyclic phosphates as the final products as demonstrated by HPLC/electrospray ionization mass spectrometry. Several mutants of the GCN4 leucine zipper are catalytically inactive, providing important negative controls and unequivocally associating the enzymatic activity with the peptide under study. The leucine zipper moiety of the human factor c-Jun as well as the entire c-Jun protein are also shown to catalyze degradation of RNA. The presented data, which was obtained in the test-tube experiments, adds GCN4 and c-Jun to the pool of proteins with multiple functions (also known as moonlighting proteins). If expressed in vivo, the endoribonuclease activity of these bZIP-containing factors may represent a direct coupling between transcription activation and controlled RNA turnover. As an additional result of this work, the retro-leucine zipper of GCN4 can be added to the list of functional retro-peptides.
Proceedings of the National Academy of Sciences, 1992
The viral Jun protein (v-Jun) transforms chicken embryo fibroblasts (CEF) more effectively than its cellular counterpart (c-Jun). In certain cell types v-Jun is also a stronger transcriptional activator than c-Jun. These functional differences between v-Jun and c-Jun result from a deletion in v-Jun (referred to as "delta deletion") that seems to weaken the interaction of Jun with a negative cellular regulator molecule. These observations suggested that the oncogenicity of v-Jun may be due to an enhanced ability to activate transcription of target genes. To test this hypothesis, we constructed several deletions in the delta domain of chicken c-Jun and determined their transforming and transactivating properties. Surprisingly, we found an inverse correlation between the ability of the mutants to transform CEF and to transactivate the collagenase and transin promoters in CEF. In contrast, there was no significant effect of the delta mutations in c-Jun on transactivation in F9 murine embryonal carcinoma cells. The function of the delta region is therefore cell-type specific. The inverse correlation between transformation and transactivation in CEF suggests that the strong growth-promoting effect of v-Jun may be related to a failure to activate the transcription of growth attenuating genes.
Molecular and Cellular Biology, 2003
Many regulatory elements in eukaryotic promoters do not correspond to optimal recognition sequences for the transcription factors that regulate promoter function by binding to the elements. The sequence of the binding site may influence the structural and functional properties of regulatory protein complexes. Fos-Jun heterodimers were found to bind nonconsensus AP-1 sites in a preferred orientation. Oriented Fos-Jun heterodimer binding was attributed to nonidentical recognition of the two half-sites by Fos and Jun. Jun bound preferentially to the consensus half-site, whereas Fos was able to bind nonconsensus half-sites. The orientation of heterodimer binding affected the transcriptional cooperativity of Fos-Jun-NFAT1 complexes at composite regulatory elements in mammalian cells. Jun dimerization with Fos versus ATF2 caused it to bind opposite half-sites at nonconsensus AP-1 elements. Similarly, ATF2 bound to opposite half-sites in Fos-ATF2-NFAT1 and ATF2-Jun-NFAT1 complexes. The orientations of nonconsensus AP-1 sites within composite regulatory elements affected the cooperativity of Fos-Jun as well as Jun-Jun binding with NFAT1. Since Jun homodimers cannot bind to AP-1 sites in a preferred orientation, the effects of the orientations of nonconsensus AP-1 sites on the stabilities of Jun-Jun-NFAT1 complexes are likely to be due to asymmetric conformational changes in the two subunits of the homodimer. Nonconsensus AP-1 site orientation also affected the synergy of transcription activation between Jun homodimers and NFAT1 at composite regulatory elements. The asymmetric recognition of nonconsensus AP-1 sites can therefore influence the transcriptional activities of Fos and Jun both through effects on the orientation of heterodimer binding and through differential conformational changes in the two subunits of the dimer.