Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

After minus-strand strong-stop DNA (-sssDNA) synthesis, the RNA template is degraded by the RNase H activity of reverse transcriptase (RT), generating a single-stranded DNA. The genomes of some retroviruses contain sequences that could lead to self-priming of their minus signsssDNA. Self-priming was prevented by annealing a DNA oligonucleotide to the 3' end of model DNAs that corresponded to the 3' ends of the -sssDNAs (-R ssDNA) from human immunodeficiency virus type 1 (HIV-1), type 2 (HIV-2), and human T-cell leukemia virus type 1 (HTLV-1) but nonspecific strand transfer to ssDNA molecules in solution was induced in vitro (Golinelli and Hughes, 2001). This nonspecific strand transfer involved the addition of a nontemplated base to the 3' end of -R ssDNAs that was part of a blunt-ended duplex. In the case of HIV-2 -R ssDNA, A and C were added more efficiently than G and T. Strand transfer to ssDNA in solution occurred only if the nontemplated base could form a basepair with the last base at the 3' end of the ssDNA. If there was a mismatch, strand transfer did not occur. There was no detectable strand transfer to internal sites in the target ssDNA except to the second position from the 3' end of the DNA acceptor when the sequences at the 3' ends of the two DNAs allowed the formation of two basepairs. The nontemplated base addition and the one-basepair strand transfer were both affected by the salt concentration in the reaction, the nature of the reverse transcriptase (HIV-1 versus Moloney murine leukemia virus), and the sequence at the 3' end of -R ssDNA. NC reduced the efficiency of nonspecific strand transfer in vitro, suggesting that NC may have a role in reducing nonspecific strand transfer in vivo.
...
PMID:Nontemplated base addition by HIV-1 RT can induce nonspecific strand transfer in vitro. 1188 71

We studied the kinetics of nontemplated nucleotide addition by the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) using model substrates derived from the 3' end of HIV-1 minus-strand strong-stop DNA. The addition of a nontemplated nucleotide was highly dependent on the nature of the base (fastest addition with dATP), type of nucleoside, and pH of the reaction buffer. The salt concentration, presence or absence of nucleocapsid protein, and nature of the blunt-ended duplex (DNA/DNA versus RNA/DNA) had only limited effects. The efficiency and base specificity were strongly affected by the sequence at the 3' end of the blunt-ended duplex. In every case, nontemplated nucleotide addition was much slower than templated polymerization. The K(d) for the incoming dNTP with an RT bound to a blunt-ended duplex was at least 1000-fold higher than with a duplex with a template overhang. At concentrations normally found in vivo, ATP can compete with dNTPs for binding to the polymerase active site and reduce the efficiency of nontemplated nucleotide addition. Although a stable ternary complex RT/DNA/dNTP could be readily detected by gel retardation assays if the DNA had a template overhang, stable ternary complexes were not observed with a blunt-ended duplex substrate. At in vivo concentrations of dNTPs (5-10 microM), nontemplated nucleotide addition occurred, but it was very inefficient and the rate of nontemplated polymerization is at least 10000-fold slower than the rate of templated polymerization. We could conclude that, in vivo, the unfavorable binding of the incoming dNTP, low concentration of dNTPs, the presence of a large concentration of ATP, and the inability to form a stable ternary complex prior to the polymerization step collaborate to reduce the efficiency of nontemplated nucleotide addition.
...
PMID:Nontemplated nucleotide addition by HIV-1 reverse transcriptase. 1198 Apr 93

The physiological effects of angiotensin II (Ang II) are mediated through specific AT(1) and AT(2) receptors. Tissue distribution and affinity of these receptors have been explored in binding studies, reverse transcriptase-polymerase chain reaction and in situ hybridisation. Sequencing has also demonstrated gene polymorphisms for both AT(1) and AT(2) receptors. Numerous potent nonpeptide antagonists of angiotensin converting enzyme or of AT receptors have been developed, thus providing a precise analysis of the physiology of the renin-angiotensin system. AT(1) receptors are widely expressed throughout adult tissues, while AT(2) receptors are mainly expressed in the fetus. Receptor density on the cell surface is regulated by multiple hormonal, cytokine and metabolic factors, and is thus profoundly affected by various pathological conditions, especially in the myocardium, kidney and blood vessels. To date, the precise molecular basis for these modifications has not been fully explained, although it may rely in part upon AT receptor gene polymorphisms, which could thus constitute increased risk factors for cardiovascular disease. AT(1) and AT(2) receptor expression is therefore influenced by both age and environmental specifications and is likely to be increased by a diet rich in salt or cholesterol, thus justifying the use of Ang II receptor antagonists in morbidity-mortality studies in high-risk patients.
...
PMID:[Exploring AT(1) and AT(2) angiotensin II receptors in humans]. 1203 85

Mice with disruption of the kinin B(2) receptor (B(2)KO mice) are sensitive to salt-rich diets, which causes hypertension. The aim of the study was to assess the role of endothelin-1 (ET-1) and angiotensin-II in hypertensive B(2)KO mice on a salt-rich diet. We also wanted to verify if there is an upregulation of the mRNA expression of the precursors or receptors for these hormones. Two groups of B(2)KO mice (20-25 g) were investigated. The first group received an 8% NaCl diet with 1% NaCl in drinking water (HS) and the second was fed with normal food with tap water (NS). The antagonists tested were the ET(A) receptor antagonist BQ-123 (1 and 5 mg/kg), the ET(B) receptor antagonist BQ-788 (0.25 and 1 mg/kg), the angiotensin receptor type 1 antagonist losartan (10 mg/kg) and the angiotensin-converting enzyme inhibitor captopril (3 mg/kg). These were injected intraperitoneally 30 min prior to blood pressure measurement by the tail-cuff method. We also studied the level of expression of preproET-1, ET-1 receptors, angiotensinogen and angiotensin receptors by RNA extraction from the heart and kidneys of these mice followed by reverse transcriptase (RT)-PCR. B(2)KO mice (HS) were hypertensive after 8 weeks compared with B(2)KO mice on normal diet (HS, 93.4+/-1.5 mmHg, n=7; NS, 61.4+/-2.7 mmHg, n=7). In the HS group, the mean arterial blood pressure was significantly reduced by BQ-123 (5 mg/kg) to 61.9+/-1.8 mmHg (n=7), by BQ-788 (1 mg/kg) to 58.8+/-2.6 mmHg (n=6), by losartan (10 mg/kg) to 73.2+/-1.7 mmHg (n=8) and by captopril (3 mg/kg) to 86.0+/-2.3 mmHg (n=8). The expression studied by RT-PCR did not show any difference (either in precursors or receptors expression) between hypertensive and normal mice. The four antagonists used seemed to reverse the hypertension. These results suggest that ET-1 and angiotensin-II are probably involved in the mechanism that leads to hypertension since the effect of these hormones is probably not compensated by kinins in B(2)KO mice. Further studies are necessary to understand the implication of the cross-talk between these hormones in the hypertensive state.
...
PMID:Role of endothelin receptors in the hypertensive state of kinin B(2) knockout mice subjected to a high-salt diet. 1219 27

Glomerular hypertension is a major determinant advancing progression to end-stage renal failure. Podocytes, which are thought to counteract pressure-mediated capillary expansion, are increasingly challenged in glomerular hypertension. Studies in animal models of glomerular hypertension indicate that glomerulosclerosis develops from adhesions of the glomerular tuft to Bowman's capsule due to progressive podocyte loss. However, the molecular alterations of podocytes in glomerular hypertension are unknown. In this study, we determined the changes in gene expression in podocytes induced by mechanical stress in vitro (cyclic biaxial stretch, 0.5 Hz, 5% linear strain, 3 days) using cDNA arrays (6144 clones). Sixteen differentially regulated genes were identified, suggesting alterations of cell-matrix interaction, mitochondrial/metabolic function, and protein synthesis/degradation in stretched podocytes. The transcript for the matricellular protein osteopontin (OPN) was most strongly up-regulated by stretch (approximately threefold). By reverse transcriptase-polymer chain reaction, up-regulation of OPN mRNA was also detected in glomeruli of rats treated for 2.5 wk with desoxycorticosterone acetate-salt, an animal model of glomerular hypertension. In cultured podocytes, OPN coating induced a motile phenotype increasing actin nucleation proteins at cell margins and reducing stress fibers and focal adhesions. Intriguingly, additional OPN coating of collagen IV-coated membranes accelerated stretch-induced actin reorganization and markedly diminished podocyte loss at higher strain. This study delineates the molecular response of podocytes to mechanical stress and identifies OPN as a stretch-adapting molecule in podocytes.
...
PMID:Analysis of differential gene expression in stretched podocytes: osteopontin enhances adaptation of podocytes to mechanical stress. 1235 96

The gram-positive, aerobic, moderately halophilic bacterium Halobacillus halophilus is challenged in its environment by frequently changing salt (NaCl) concentrations. Recently, H. halophilus was shown to be the first prokaryote that is dependent on Cl(-) for growth. In a search for the biological function of Cl(-) in this prokaryote, we identified different Cl(-)-dependent processes, which suggests a more general role for Cl(-) in the metabolism of H. halophilus. To analyze the effect of Cl(-) in more detail, we concentrated on one model system, the Cl(-)-dependent production of flagella, and aimed to identify the molecular basis for the Cl(-) dependence of flagellum production. Here, we report that synthesis of the major subunit of the flagellum, FliC, is dependent on the Cl(-) concentration of the medium, as determined by Western blot analyses. The gene encoding FliC was cloned and sequenced, and Northern blot as well as reverse transcriptase PCR analyses revealed that expression of fliC is Cl(-) dependent. FliC is the first protein of known function demonstrated to be synthesized in a Cl(-)-dependent manner in a prokaryote. Two-dimensional gel electrophoresis of cells grown under different conditions revealed five more Cl(-)-induced proteins; these were identified by N-terminal sequencing and database searches to be orthologs of proteins involved in stress response in Bacillus subtilis. The data indicate that Cl(-) is an important environmental signal in this moderate halophile and regulates protein synthesis and gene expression. Furthermore, the data may suggest that Cl(-) plays a role in the signal transduction involved in salt perception by this bacterium.
...
PMID:Chloride, a new environmental signal molecule involved in gene regulation in a moderately halophilic bacterium, Halobacillus halophilus. 1239 91

Guanylyl cyclase C (GC-C) is a membrane-associated form of guanylyl cyclase and serves as the receptor for the heat-stable enterotoxin (ST) peptide and endogenous ligands guanylin, uroguanylin, and lymphoguanylin. The major site of expression of GC-C is the intestinal epithelial cell, although GC-C is also expressed in extraintestinal tissue such as the kidney, airway epithelium, perinatal liver, stomach, brain, and adrenal glands. Binding of ligands to GC-C leads to accumulation of intracellular cGMP, the activation of protein kinases G and A, and phosphorylation of the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel that regulates salt and water secretion. We examined the expression of GC-C and its ligands in various tissues of the reproductive tract of the rat. Using reverse transcriptase and the polymerase chain reaction, we demonstrated the presence of GC-C, uroguanylin, and guanylin mRNA in both male and female reproductive organs. Western blot analysis using a monoclonal antibody to GC-C revealed the presence of differentially glycosylated forms of GC-C in the caput and cauda epididymis. Exogenous addition of uroguanylin to minced epididymal tissue resulted in cGMP accumulation, suggesting an autocrine or endocrine activation of GC-C in this tissue. Immunohistochemical analyses demonstrated expression of GC-C in the tubular epithelial cells of both the caput epididymis and cauda epididymis. Our results suggest that the GC-C signaling pathway could converge on CFTR in the epididymis and perhaps control fluid and ion balance for optimal sperm maturation and storage in this tissue.
...
PMID:Expression of the receptor guanylyl cyclase C and its ligands in reproductive tissues of the rat: a potential role for a novel signaling pathway in the epididymis. 1244 76

Defensins are antimicrobial peptides that play a major role in innate immunity. Using reverse transcriptase-polymerase chain reaction, immunochemistry, or both, we performed a search of all presently known defensins in rat testis, epididymis, and isolated testicular cells; in mouse testis and epididymis; and in human testis and ejaculates. In the rat, all alpha- and beta-defensins except RNP-4 were expressed within the testis, whereas alpha-defensins RNP1-2, RNP-4, and beta-defensins RBD-1 and RBD-2 were present within the epididymis. In the mouse, the cryptdin transcripts CRS1C, mBD-1, and mBD-2 were detected in the testis and epididymis, whereas mBD-3 and mBD-4 were expressed only in the epididymis, and CRS4C was absent in both organs. In the human testis, transcripts for four known defensins were expressed with the consistent exception of HBD-2 and HBD-3. In rat interstitial tissue, resident macrophages expressed most of the defensins studied, whereas Leydig cells produced only RBD-2. In contrast, all studied defensins except RNP-4 were present in the seminiferous tubules. Within these tubules, peritubular and Sertoli cells expressed most of the studied alpha- and beta-defensins, whereas spermatogonia displayed only alpha-defensins, but at relatively high levels. Meiotic pachytene spermatocytes expressed only beta-defensins, whereas postmeiotic spermatids and their cytoplasmic lobes displayed both types. In humans, the HBD-1 peptide was expressed mainly in the germ line from pachytene spermatocytes to late spermatids. The peptide was also present in ejaculated spermatozoa and seminal plasma, where multiple soluble forms were present. Finally, high salt concentration or dithiothreitol-sensitive cationic extracts from human seminal plasma were indeed found to display antimicrobial activity. We conclude that the male reproductive tract produces defensins that most probably assume an important, innate organ defense system against pathogens.
...
PMID:Expression of antimicrobial defensins in the male reproductive tract of rats, mice, and humans. 1249

Uroguanylin, a peptide hormone highly expressed in the gastrointestinal tract, is implicated in the regulation of epithelial salt and water transport processes. Since little is known about a possible role of uroguanylin in the reproductive system, we investigated for the first time the occurrence of this peptide in the human prostate using specimens of benign prostatic hyperplasia. Northern blot analyses detected a single uroguanylin transcript of approximately 600 bp in prostate RNA. The uroguanylin expression was further investigated by reverse transcriptase polymerase chain reaction of prostate RNA with uroguanylin-specific primers. Sequencing of the fragments obtained indicated the presence of a uroguanylin molecule with a sequence identical to its intestinal counterpart. Furthermore, in situ hybridization and immunohistochemistry revealed that uroguanylin mRNA and peptide are confined to epithelial cells of the prostate glands. Comparison with the distribution pattern of immunoreactivity for prostate-specific antigen (PSA) showed a high degree of colocalization of uroguanylin- and PSA-immunoreactive cells. In addition, by western blotting techniques we detected the presence of high molecular weight uroguanylin-immunoreactive material in prostatic fluid. In conclusion, our study indicates that the human prostate glands synthesize and secrete (pro-)uroguanylin. We hypothesize that this hormone may play a novel role in the male reproductive tract.
...
PMID:Occurrence and localization of uroguanylin in the aging human prostate. 1254 7

The human immunodeficiency virus (HIV) epidemic is an important medical problem. Although combination drug regimens have produced dramatic decreases in viral load, current therapies do not provide a cure for HIV infection. We have used structure-based design and combinatorial medicinal chemistry to identify potent and selective HIV-1 reverse transcriptase (RT) inhibitors that may work by a mechanism distinct from that of current HIV drugs. The most potent of these compounds (compound 4, 2-naphthalenesulfonic acid, 4-hydroxy-7-[[[[5-hydroxy-6-[(4-cinnamylphenyl)azo]-7-sulfo-2-naphthalenyl]amino]carbonyl]amino]-3-[(4-cinnamylphenyl)azo], disodium salt) has an IC(50) of 90 nM for inhibition of polymerase chain extension, a K(d) of 40 nM for inhibition of DNA-RT binding, and an IC(50) of 25-100 nM for inhibition of RNaseH cleavage. The parent compound (1) was as effective against 10 nucleoside and non-nucleoside resistant HIV-1 RT mutants as it was against the wild-type enzyme. Compound 4 inhibited HIV-1 RT and murine leukemia virus (MLV) RT, but it did not inhibit T(4) DNA polymerase, T(7) DNA polymerase, or the Klenow fragment at concentrations up to 200 nM. Finally, compound 4 protected cells from HIV-1 infection at a concentration more than 40 times lower than the concentration at which it caused cellular toxicity.
...
PMID:A novel mechanism for inhibition of HIV-1 reverse transcriptase. 1264 28


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---