Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have purified DNA-dependent RNA polymerase II from Candida albicans, a human pathogenic yeast. The enzyme consists of 9 polypeptides that are unique to C. albicans, their mobility on SDS-PAGE being different from the mobility of the corresponding subunits of RNA polymerase II from Saccharomyces cerevisiae or C. utilis. In the present study we also demonstrate that RNA pol II from C. albican and C. utilis are metalloproteins containing approximately 5 mol of zinc per mole of enzyme. Although prolonged dialysis in 10 or 20 mM EDTA failed to remove Zn(II) from the C. albicans enzyme, in the C. utilis enzyme 3 Zn(II) ions could be removed and then reconstituted in the presence of excess Zn(II). o-Phenanthroline (5 mM) removed Zn(II) from C. albicans enzyme irreversibly in a time-dependent fashion with concomitant loss of enzyme activity. Circular dichroism studies revealed structural changes on removal of zinc, thus suggesting a role for Zn in maintenance of structural stability. Further, we demonstrate that the largest subunit of the C. utilis enzyme and the 3 large subunits of the C. albicans enzyme can bind radioactive zinc.
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PMID:DNA-dependent RNA polymerase II from Candida species is a multiple zinc-containing metalloenzyme. 1079 92

The TATA-binding protein (TBP) in the TFIID complex binds specifically to the TATA-box to initiate the stepwise assembly of the preinitiation complex (PIC) for RNA polymerase II transcription. Transcriptional activators and repressors compete with general transcription factors at each step to influence the course of the assembly. To investigate this process, the TBP.TATA complex was titrated with HMG-1 and the interaction monitored by electrophoretic mobility shift assays. The titration produced a ternary HMG-1.TBP. TATA complex, which exhibits increased mobility relative to the TBP. TATA complex. The addition of increasing levels of TFIIB to this complex results in the formation of the TFIIB.TBP.TATA complex. However, in the reverse titration, with very high mole ratios of HMG-1 present, TFIIB is not dissociated off and a complex is formed that contains all factors. The simultaneous addition of E1A to a mixture of TBP and TATA; or HMG-1, TBP, and TATA; or TFIIB, TBP, and TATA inhibits complex formation. On the other hand, E1A added to the pre-established complexes shows a significantly reduced capability to disrupt the complex. In add-back experiments with all complexes, increased levels of TBP re-established the complexes, indicating that the primary target for E1A in all complexes is TBP.
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PMID:Influence of HMG-1 and adenovirus oncoprotein E1A on early stages of transcriptional preinitiation complex assembly. 1088 37

Binding of the TATA-binding protein (TBP) to promoter DNA bearing the TATA sequence is an obligatory initial step in RNA polymerase II transcription initiation. The interactions of Saccharomyces cerevisiae TBP with the E4 (TATATATA) and adenovirus major late (TATAAAAG) promoters have been modeled via global analysis of kinetic and thermodynamic data obtained using fluorescence resonance energy transfer. A linear two-intermediate kinetic mechanism describes the reaction of both of these consensus strong promoters with TBP. Qualitative features common to both interactions include tightly bound TBP-DNA complexes with similar solution geometries, simultaneous DNA binding and bending, and the presence of intermediate TBP-DNA conformers at high mole fraction throughout most of the reaction and at equilibrium. Despite very similar energetic changes overall, the stepwise entropic and enthalpic compensations along the two pathways differ markedly following the initial binding/bending event. Furthermore, TBP-E4 dissociation ensues from both replacement and displacement processes, in contrast to replacement alone for TBP-adenovirus major late promoter. A model is proposed that explicitly correlates these similarities and differences with the sequence-specific structural properties inherent to each promoter. This detailed mechanistic comparison of two strong promoters interacting with TBP provides a foundation for subsequent comparison between consensus and variant promoter sequences reacting with TBP.
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PMID:Marked stepwise differences within a common kinetic mechanism characterize TATA-binding protein interactions with two consensus promoters. 1138 41

Polycomb group (PcG) proteins such as Enhancer of zeste homolog 2 (EZH2) are epigenetic transcriptional repressors that function through recognition and modification of histone methylation and chromatin structure. Targets of PcG include cell cycle regulatory proteins which govern cell cycle progression and cellular senescence. Senescence is a characteristic of melanocytic nevi, benign melanocytic proliferations that can be precursors of malignant melanoma. In this study, we report that EZH2, which we find absent in melanocytic nevi but expressed in many or most metastatic melanoma cells, functionally suppresses the senescent state in human melanoma cells. EZH2 depletion in melanoma cells inhibits cell proliferation, restores features of a cellular senescence phenotype, and inhibits growth of melanoma xenografts in vivo. p21/CDKN1A is activated upon EZH2 knockdown in a p53-independent manner and contributes substantially to cell cycle arrest and induction of a senescence phenotype. EZH2 depletion removes histone deacetylase 1 (HDAC1) from the CDKN1A transcriptional start site and downstream region, enhancing histone 3 acetylation globally and at CDKN1A. This results in recruitment of RNA polymerase II, leading to p21/CDKN1A activation. Depletion of EZH2 synergistically activates p21/CDKN1A expression in combination with the HDAC inhibitor trichostatin A. Since melanomas often retain wild-type p53 function activating p21, our findings describe a novel mechanism whereby EZH2 activation during tumor progression represses p21, leading to suppression of cellular senescence and enhanced tumorigenicity.
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PMID:EZH2-dependent suppression of a cellular senescence phenotype in melanoma cells by inhibition of p21/CDKN1A expression. 2138 5

Although activating BRAF/NRAS mutations are frequently seen in melanomas, they are not sufficient to drive malignant transformation and require additional events. Frequent co-occurrence of mutations in the promoter for telomerase reverse transcriptase (TERT), along with BRAF alterations, has recently been noted and correlated with poorer prognosis, implicating a functional link between BRAF signaling and telomerase reactivation in melanomas. Here, we report that RAS-ERK signaling in BRAF mutant melanomas is critical for regulating active chromatin state and recruitment of RNA polymerase II at mutant TERT promoters. Our study provides evidence that the mutant TERT promoter is a key substrate downstream of the RAS-ERK pathway. Reactivating TERT and hence reconstituting telomerase is an important step in melanoma progression from nonmalignant nevi with BRAF mutations. Hence, combined targeting of RAS-ERK and TERT promoter remodeling is a promising avenue to limit long-term survival of a majority of melanomas that harbor these two mutations.
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PMID:Activation of mutant TERT promoter by RAS-ERK signaling is a key step in malignant progression of BRAF-mutant human melanomas. 2791 94