Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rhizobium meliloti C4-dicarboxylic acid transport protein D (DCTD) activates transcription by a form of RNA polymerase holoenzyme that has sigma 54 as its sigma factor (referred to as E sigma 54). DCTD catalyzes the ATP-dependent isomerization of closed complexes between E sigma 54 and the dctA promoter to transcriptionally productive open complexes. Transcriptional activation probably involves specific protein-protein interactions between DCTD and E sigma 54. Interactions between sigma 54-dependent activators and E sigma 54 are transient, and there has been no report of a biochemical assay for contact between E sigma 54 and any activator to date. Heterobifunctional crosslinking reagents were used to examine protein-protein interactions between the various subunits of E sigma 54 and DCTD. DCTD was crosslinked to Salmonella typhimurium sigma 54 with the crosslinking reagents succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate and N-hydroxysulfosuccinimidyl-4-azidobenzoate. Cys-307 of sigma 54 was identified by site-directed mutagenesis as the residue that was crosslinked to DCTD. DCTD was also crosslinked to the beta subunit of Escherichia coli core RNA polymerase with succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate, but not with N-hydroxysulfosuccinimidyl-4-azidobenzoate. These data suggest that interactions of DCTD with sigma 54 and the beta subunit may be important for transcriptional activation and offer evidence for interactions between a sigma 54-dependent activator and sigma 54, as well as the beta subunit of RNA polymerase.
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PMID:Protein crosslinking studies suggest that Rhizobium meliloti C4-dicarboxylic acid transport protein D, a sigma 54-dependent transcriptional activator, interacts with sigma 54 and the beta subunit of RNA polymerase. 756 1

Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is an inhibitor of positive transcription elongation factor b (P-TEFb) that has recently been shown to be involved in cancers, AIDS, cardiac hypertrophy and inflammation. It was first cloned from vascular smooth muscle cells (VSMCs) treated with hexamethylene bis-acetamide (HMBA), a compound that suppresses the proliferation of VSMCs. Little was kappanown about the biological function of HEXIM1 till the discovery of its association with P-TEFb. P-TEFb, a protein complex composed of cyclin-dependent kinase 9 and a cyclin partner, plays a key role in regulation of RNA polymerase II elongation. When associated with 7SK small nuclear RNA, HEXIM1 binds to P-TEFb and inhibits the kinase activity of P-TEFb. This finding provides the molecular basis for the inhibitory function of HEXIM1 in P-TEFb-dependent transcription, such as human immunodeficiency virus Tat transactivation and NFkappaB-mediated transcription. Recent evidences suggest an essential role of HEXIM1 in several diseases through transcriptional regulation.
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PMID:HEXIM1 and the control of transcription elongation: from cancer and inflammation to AIDS and cardiac hypertrophy. 1767 21

Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is an inhibitor of the positive transcription elongation factor b (P-TEFb), which controls RNA polymerase II transcription and human immunodeficiency virus Tat transactivation. In cells, more than half of P-TEFb is associated with HEXIM1 resulting in the inactivation of P-TEFb. Recently, we found that nucleophosmin (NPM), a key factor involved in p53 signaling pathway, interacts with HEXIM1 and activates P-TEFb-dependent transcription. Here we report that human double minute-2 protein (HDM2), a p53-specific E3 ubiquitin ligase, specifically ubiquitinates HEXIM1 through the lysine residues located within the basic region of HEXIM1. However, the HDM2-induced HEXIM1 ubiquitination does not lead to proteasome-mediated protein degradation. Fusion of ubiquitin to HEXIM1 demonstrates stronger inhibition on P-TEFb-dependent transcription. Our results demonstrate that HDM2 functions as a specific E3 ubiquitin ligase for HEXIM1, suggesting a possible role for HEXIM1 ubiquitination in the regulation of P-TEFb activity.
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PMID:Ubiquitination of HEXIM1 by HDM2. 1968 63

Right ventricular hypertrophy (RVH) and right ventricular (RV) contractile dysfunction are major determinants of prognosis in pulmonary arterial hypertension (PAH) and PAH remains a severe disease. Recently, direct interruption of left ventricular hypertrophy has been suggested to decrease the risk of left-sided heart failure. Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is a negative regulator of positive transcription elongation factor b (P-TEFb), which activates RNA polymerase II (RNAPII)-dependent transcription and whose activation is strongly associated with left ventricular hypertrophy. We hypothesized that during the progression of PAH, increased P-TEFb activity might also play a role in RVH, and that HEXIM1 might have a preventive role against such process. We revealed that, in the mouse heart, HEXIM1 is highly expressed in the early postnatal period and its expression is gradually decreased, and that prostaglandin I(2), a therapeutic drug for PAH, increases HEXIM1 levels in cardiomyocytes. These results suggest that HEXIM1 might possess negative effect on cardiomyocyte growth and take part in cardiomyocyte regulation in RV. Using adenovirus-mediated gene delivery to cultured rat cardiomyocytes, we revealed that overexpression of HEXIM1 prevents endothelin-1-induced phosphorylation of RNAPII, cardiomyocyte hypertrophy, and mRNA expression of hypertrophic genes, whereas a HEXIM1 mutant lacking central basic region, which diminishes P-TEFb-suppressing activity, could not. Moreover, we created cardiomyocyte-specific HEXIM1 transgenic mice and revealed that HEXIM1 ameliorates RVH and prevents RV dilatation in hypoxia-induced PAH model. Taken together, these findings indicate that cardiomyocyte-specific overexpression of HEXIM1 inhibits progression to RVH under chronic hypoxia, most possibly via inhibition of P-TEFb-mediated enlargement of cardiomyocytes. We conclude that P-TEFb/HEXIM1-dependent transcriptional regulation may play a pathophysiological role in RVH and be a novel therapeutic target for mitigating RVH in PAH.
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PMID:Cardiomyocyte-specific overexpression of HEXIM1 prevents right ventricular hypertrophy in hypoxia-induced pulmonary hypertension in mice. 2330 Jun 97

The incorporation of brominated flame retardants into industrial and household appliances has increased their occurrence in the environment, resulting in deleterious effects on wildlife. With the increasing restraints on available compounds, there has been a shift to using brominated flame retardants that has seen the production of alternative brominated flame retardants such as 1,2-dibromo-4-(1,2 dibromoethyl) cyclohexane (TBECH), which has been detected in the environment. In previous in silico and in vitro studies the authors have shown that TBECH can activate both the human androgen receptor (hAR) and the zebrafish AR (zAR) suggesting that it is a potential endocrine disruptor. The present study was aimed at determining the interaction of TBECH with the chicken AR (cAR). In the present study, TBECH bound to cAR, but in vitro activation assay studies using the chicken LMH cell line showed it had a potency of only 15% compared with testosterone. Sequence difference between ARs from different species may contribute to the different responses to TBECH. Further quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) analysis showed that TBECH interacted with and altered the expression of both thyroid receptors and estrogen receptors. In addition, the qRT-PCR analysis showed that TBECH altered the transcription pattern of genes involved in inflammatory, apoptotic, proliferative, DNA methylation, and drug-metabolizing pathways. This demonstrates that TBECH, apart from activating cAR, can also influence multiple biological pathways in the chicken.
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PMID:1,2-Dibromo-4-(1,2 dibromoethyl) cyclohexane (TBECH)-mediated steroid hormone receptor activation and gene regulation in chicken LMH cells. 2437 16

Here, we report a novel antibody drug conjugate (ADC) with the humanized anti-CD26 monoclonal antibody YS110 and triptolide (TR-1). YS110 has an inhibitory activity against the CD26-positive tumor growth via the immunological and direct pathway, such as intra-nuclear transportation of CD26 and YS110, and suppressed transcription of RNA polymerase II (Pol II) subunit POLR2A. The ADC conjugated with YS110 and an antitumor compound triptolide (TR-1), which is an inhibitor for TFIIH, one of the general transcription factors for Pol II was developed. YS110 and triptolide were crosslinked by the heterobifunctional linker succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) and designated Y-TR1. Antitumor efficacy of Y-TR1 against malignant mesothelioma and leukemia cell lines were assessed by the in vitro cell viability assay and in vivo assay using xenografted mouse models. Y-TR1 showed significant cytotoxicity against CD26-positive cell lines but not CD26-negative counterparts in a dose-dependent manner via suppression of mRNA synthesis by impairment of the Pol II activity. The tumors in xenografted mice administered Y-TR1 was smaller than that of the unconjugated YS110 treated mice without severe toxicity. In conclusion, the novel compound Y-TR1 showed antitumor properties against CD26-positive cancer cell lines both in vitro and in vivo without toxicity. The Y-TR1 is a unique antitumor ADC and functions against Pol II.
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PMID:Novel Antibody-Drug Conjugate with Anti-CD26 Humanized Monoclonal Antibody and Transcription Factor IIH (TFIIH) Inhibitor, Triptolide, Inhibits Tumor Growth via Impairing mRNA Synthesis. 3139 54