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)

The porphyrin-heme pathway is controlled in the liver at the level of the mitochondrial enzyme delta-aminolevulinate synthase (EC 2.3.1.37), a protein inducible in cultured avian hepatocytes by a variety of chemicals including certain 5beta-metabolites of steroid hormones. The great sensitivity of the induction process to inhibition by agents known to block transcriptional activity of genetic material suggests that some control mechanism may be operating at this level to regulate the formation of the enzyme. We report here enhancement of nuclear RNA synthesis and of Mn(2+)-(NH(4))(2)SO(4)-stimulated DNA-dependent RNA polymerase (EC 2.7.7.6) activities by the 5beta-steroid metabolite, 3alpha-hydroxy-5beta-androstan-17-one (etiocholanolone), in cultured avian hepatocytes during induction of the enzyme. These changes were demonstrated in the G(1) phase of the hepatocyte cell cycle at a time when DNA synthesis is constant. Our findings support the view that one of the early steps in the process of induction of delta-aminolevulinate synthase by steroid metabolites requires new RNA synthesis, very probably messenger RNA, suggesting a 5beta-steroid transcriptional control mechanism for induction of this protein.
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PMID:Enhancement of RNA synthesis in avian liver cell cultures by a 5beta-steroid metabolite during induction of delta-aminolevulinate synthase. 452 7

Heme is an essential prosthetic group of proteins involved in oxygen transport, energy metabolism and nitric oxide production. ALAS1 (5-aminolevulinate synthase) is the rate-limiting enzyme in heme synthesis in the liver and is highly regulated to adapt to the metabolic demand of the hepatocyte. In the present study, we describe human hepatic ALAS1 as a new direct target for the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARalpha). In primary human hepatocytes and in HepG2 cells, PPARalpha agonists induced an increase in ALAS1 mRNA levels, which was abolished by PPARalpha silencing. These effects are mediated by two functional PPAR binding sites at positions -9 and -2.3 kb relative to the ALAS1 transcription start site. PPARalpha ligand treatment also up-regulated the mRNA levels of the genes ALAD (5-aminolevulinate dehydratase), UROS (uroporphyrinogen III synthase), UROD (uroporphyrinogen decarboxylase), CPOX (coproporphyrinogen oxidase) and PPOX (protoporphyrinogen oxidase) encoding for enzymes controlling further steps in heme biosynthesis. In HepG2 cells treated with PPARalpha agonists and in mouse liver upon fasting, the association of PPARalpha, its partner retinoid X receptor, PPARgamma co-activator 1alpha and activated RNA polymerase II with the transcription start site region of all six genes was increased, leading to higher levels of the metabolite heme. In conclusion, these data strongly support a role of PPARalpha in the regulation of human ALAS1 and of five additional genes of the pathway, consequently leading to increased heme synthesis.
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PMID:Peroxisome proliferator-activated receptor alpha controls hepatic heme biosynthesis through ALAS1. 2107 84

T7 RNA polymerase (T7RNAP) and T7 promoter are powerful genetic components, thus a plasmid-driven T7 (PDT7) genetic circuit could be broadly applied for synthetic biology. However, the limited knowledge of the toxicity and instability of such a system still restricts its application. Herein, we constructed 16 constitutive genetic circuts of PDT7 and investigated the orthogonal effects in toxicity and instability. The T7 toxicity was elucidated from the construction processes and cell growth characterization, showing the importance of optimal orthogonality for PDT7. Besides, a protein analysis was performed to validate how the T7 system affected cell metabolism and led to the instability. The application of constitutive PDT7 in functional protein expressions, including carbonic anhydrase, lysine decarboxylase, and 5-ALA synthetase was demonstrated. Furthermore, PDT7 working as a genetic amplifier had been designed for E. coli cell-based biosensors, which illustrated the opportunities in the future of PDT7 used in synthetic biology.
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PMID:New Insight into Plasmid-Driven T7 RNA Polymerase in Escherichia coli and Use as a Genetic Amplifier for a Biosensor. 3214 3