Phosphorylation of yeast TBP by protein kinase CK2 reduces its specific binding to DNA. (1/810)

Protein kinase CK2 is a ubiquitous Ser/Thr kinase which phosphorylates a large number of proteins including several transcription factors. Recombinant Xenopus laevis CK2 phosphorylates both recombinant Saccharomyces cerevisiae and Schizosaccharomyces pombe TATA binding protein (TBP). The phosphorylation of TBP by CK2 reduces its binding activity to the TATA box. CK2 copurifies with the transcription factor IID (TFIID) complex from HeLa cell extracts and phosphorylates several of the TBP-associated factors within TFIID. Taken together these findings argue for a role of CK2 in the control of transcription by RNA polymerase II through the modulation of the binding activity of TBP to the TATA box.  (+info)

Thyroid hormone receptor-associated proteins and general positive cofactors mediate thyroid hormone receptor function in the absence of the TATA box-binding protein-associated factors of TFIID. (2/810)

Coactivators previously implicated in ligand-dependent activation functions by thyroid hormone receptor (TR) include p300 and CREB-binding protein (CBP), the steroid receptor coactivator-1 (SRC-1)-related family of proteins, and the multicomponent TR-associated protein (TRAP) complex. Here we show that two positive cofactors (PC2 and PC4) derived from the upstream stimulatory activity (USA) cofactor fraction act synergistically to mediate thyroid hormone (T3)-dependent activation either by TR or by a TR-TRAP complex in an in vitro system reconstituted with purified factors and DNA templates. Significantly, the TRAP-mediated enhancement of activation by TR does not require the TATA box-binding protein-associated factors of TFIID. Furthermore, neither the pleiotropic coactivators CBP and p300 nor members of the SRC-1 family were detected in either the TR-TRAP complex or the other components of the in vitro assay system. These results show that activation by TR at the level of naked DNA templates is enhanced by cooperative functions of the TRAP coactivators and the general coactivators PC2 and PC4, and they further indicate a potential functional redundancy between TRAPs and TATA box-binding protein-associated factors in TFIID. In conjunction with earlier studies on other nuclear receptor-interacting cofactors, the present study also suggests a multistep pathway, involving distinct sets of cofactors, for activation of hormone responsive genes.  (+info)

TAFII250, Egr-1, and D-type cyclin expression in mice and neonatal rat cardiomyocytes treated with doxorubicin. (3/810)

Differential display identified that gene fragment HA220 homologous to the transcriptional activator factor II 250 (TAFII250) gene, or CCG1, was increased in hypertrophied rodent heart. To determine whether TAFII250 gene expression is modified after cardiac damage, we measured TAFII250 expression in vivo in mouse hearts after injection of the cardiotoxic agent doxorubicin (DXR) and in vitro in DXR-treated isolated rat neonatal cardiomyocytes. In vivo atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), Egr-1, and TAFII250 expression increased with dose and time after a single DXR injection, but only ANF and beta-MHC expression were increased after multiple injections. After DXR treatment of neonatal cardiomyocytes we found decreased ANF, alpha-MHC, Egr-1, and TAFII250 expression. Expression of the TAFII250-regulated genes, the D-type cyclins, was increased after a single injection in adult mice and was decreased in DXR-treated cardiomyocytes. Thus expression of Erg-1, TAFII250, and the D-type cyclins is modulated after cardiotoxic damage in adult and neonatal heart.  (+info)

Inhibition of hTAFII32-binding implicated in the transcriptional repression by central regions of mutant p53 proteins. (4/810)

We previously identified a movable and regulable inactivation function within the central region (CRts247) of a temperature-sensitive p53 (p53(ts)) mutant, p53(N247I). Here we showed that central regions from several p53(ts) mutants behaved similarly, i.e. they repressed a neighboring activation domain only when existing in the mutant status. Using chimeric protein GAL4VP16-CRts247 as an example, we demonstrated that de novo protein synthesis was not required for the reactivation of the chimeric protein, indicating that a post-translational mechanism was involved in the control of CRts247 activity. The CRts247-conferred thermo-regulability did not work via a mechanism demanding either an alteration of the subcellular compartmentalization of or the inactivation of DNA-binding activity of the GAL4 chimera. Further, CRts247 did not function in trans, eliminating the possibility that the observed repression was because of the competition for a putative factor(s) by the mutant p53 domain. Rather, CRts247 bestowed temperature-dependent interaction with hTAFII32 to the VP16 activation domain. In a parallel experiment, CRts247 also caused a large reduction in the affinity of hTAFII32 to the p53 activation domain at the nonpermissive temperature. These results strongly suggested that inhibition of hTAFII32 binding could be one of the mechanisms responsible for the transcriptional repression by mutant p53 central regions.  (+info)

Mechanism of transcriptional repression of E2F by the retinoblastoma tumor suppressor protein. (5/810)

The retinoblastoma tumor suppressor protein (pRB) is a transcriptional repressor, critical for normal cell cycle progression. We have undertaken studies using a highly purified reconstituted in vitro transcription system to demonstrate how pRB can repress transcriptional activation mediated by the E2F transcription factor. Remarkably, E2F activation became resistant to pRB-mediated repression after the establishment of a partial (TFIIA/TFIID) preinitiation complex (PIC). DNase I footprinting studies suggest that E2F recruits TFIID to the promoter in a step that also requires TFIIA and confirm that recruitment of the PIC by E2F is blocked by pRB. These studies suggest a detailed mechanism by which E2F activates and pRB represses transcription without the requirement of histone-modifying enzymes.  (+info)

Multiple layers of cooperativity regulate enhanceosome-responsive RNA polymerase II transcription complex assembly. (6/810)

Two coordinate forms of transcriptional synergy mediate eukaryotic gene regulation: the greater-than-additive transcriptional response to multiple promoter-bound activators, and the sigmoidal response to increasing activator concentration. The mechanism underlying the sigmoidal response has not been elucidated but is almost certainly founded on the cooperative binding of activators and the general machinery to DNA. Here we explore that mechanism by using highly purified transcription factor preparations and a strong Epstein-Barr virus promoter, BHLF-1, regulated by the virally encoded activator ZEBRA. We demonstrate that two layers of cooperative binding govern transcription complex assembly. First, the architectural proteins HMG-1 and -2 mediate cooperative formation of an enhanceosome containing ZEBRA and cellular Sp1. This enhanceosome then recruits transcription factor IIA (TFIIA) and TFIID to the promoter to form the DA complex. The DA complex, however, stimulates assembly of the enhanceosome itself such that the entire reaction can occur in a highly concerted manner. The data reveal the importance of reciprocal cooperative interactions among activators and the general machinery in eukaryotic gene regulation.  (+info)

An activator binding module of yeast RNA polymerase II holoenzyme. (7/810)

The Mediator complex of Saccharomyces cerevisiae is required for both general and regulated transcription of RNA polymerase II (PolII) and is composed of two stable subcomplexes (Srb4 and Rgr1 subcomplexes). To decipher the function of each Mediator subcomplex and to delineate the functional relationship between the subcomplexes, we characterized the compositions and biochemical activities of PolII-Mediator complexes (holoenzymes) prepared from several Mediator mutant strains of S. cerevisiae. We found that holoenzymes devoid of a functional Gal11 module were defective for activated but not basal transcription in a reconstituted in vitro system. This activation-specific defect was correlated with a crippled physical interaction to transcriptional activator proteins, which could be bypassed by artificial recruitment of a mutant holoenzyme to a promoter. Consistent with this observation, a direct interaction between Gal11 and gene-specific transcriptional activator proteins was detected by far-Western analyses and column binding assays. In contrast, the srb5 deletion mutant holoenzyme was defective for both basal and activated transcription, despite its capacity for activator binding that is comparable to that of the wild-type holoenzyme. These results demonstrate that the Gal11 module of the Rgr1 subcomplex is required for the efficient recruitment of PolII holoenzyme to a promoter via activator-specific interactions, while the Srb4 subcomplex functions in the modulation of general polymerase activity.  (+info)

Overexpression of D-type cyclins, E2F-1, SV40 large T antigen and HPV16 E7 rescue cell cycle arrest of tsBN462 cells caused by the CCG1/TAF(II)250 mutation. (8/810)

tsBN462 cells, which have a point mutation in CCG1/TAF(II)250, a component of TFIID complex, arrest in G1 at the nonpermissive temperature of 39.5 degrees C. Overexpression of D-type cyclins rescued the cell cycle arrest of tsBN462 cells, suggesting that the cell cycle arrest was through Rb. Consistent with this, overexpression of E2F-1, whose function is repressed by the hypophosphorylated form of Rb, also rescued the cell cycle arrest. Moreover, expression of the viral oncoproteins SV40 large T antigen and HPV16 E7, which both bind Rb and inactivate its function, rescued the cell cycle arrest, whereas HPV16 E6 did not. Mutation of the Rb-binding motif in E7 abrogated its ability to rescue the cell cycle arrest. Expression of exogenous cyclin D1, SV40 large T antigen or CCG1/TAF(II)250 increased cyclin A expression at 39.5 degrees C. Coexpression of HPV16 E7 and adenovirus E1b19K, which blocks apoptosis, rescued the proliferation of tsBN462 cells at 38.5 degrees C. To investigate the mechanism underlying the lack of cyclin D1 expression, deletion analysis of cyclin D1 promoter was performed. The 0.15 kbp cyclin D1 core promoter region, which lacks any transcription factor binding motifs, still exhibited a temperature-sensitive phenotype in tsBN462 cells suggesting that CCG1/TAF(II)250 is critical for the function of the cyclin D1 core promoter.  (+info)