Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the heart, mRNA accumulations for sarcomeric actins and myosin heavy chains (MHC) are subject to diverse regulatorial processes. To study cardiac contractile protein transcriptional regulations, an in vitro transcription system using nonenzymatically isolated rat cardiac nuclei was characterized. Transcription was shown to be rapid and continuous during the first 20 min of incubation and 5.4-fold less than that seen from comparably isolated hepatocyte nuclei. Neither RNase nor DNase activities were detectable. Direct transcriptional analyses of the alpha- and beta-MHC and cardiac and skeletal alpha-actin genes from cardiac nuclei were performed. In 23-24-day-old rats, significant levels of transcription were seen for alpha-MHC and for the sarcomeric alpha-actins. beta-MHC was just detectable, and no positive signals were ever seen for fibronectin. We then compared the perecentages of MHC and sarcomeric alpha-actin expressions determined from 1) the transcriptional assays and 2) total isolated RNA (alpha-MHC: 90.1 +/- 4.8% (transcription), 93.0 +/- 4.7% (accumulation); beta-MHC: 9.9 +/- 4.8%, 7.0 +/- 4.7%; cardiac alpha-actin: 84.0 +/- 2.5%, 84.9 +/- 2.5%; skeletal alpha-actin: 16.1 +/- 2.5%, 15.0 +/- 2.5%). The results support the conclusion that the primary mechanisms controlling the accumulations of these gene products are transcriptional. Additionally, we show that an anti-sense mRNA showing strong homology or identity with the 5' end of the beta-MHC gene is transcribed in cardiac nuclei but not in hepatocyte nuclei.
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PMID:Cardiac expressions of alpha- and beta-myosin heavy chains and sarcomeric alpha-actins are regulated through transcriptional mechanisms. Results from nuclear run-on assays in isolated rat cardiac nuclei. 161 95

In the axolotl, Ambystoma mexicanum, a recessive cardiac lethal mutation causes an incomplete differentiation of the myocardium. Mutant hearts do not contain sarcomeric myofibrils nor do they beat. We have previously shown that normal anterior endoderm, medium conditioned by endoderm, or total RNA extracted from endoderm stimulates differentiation of mutant hearts in culture as indicated by the presence of organized myofibrils and rhythmic contractions of the "rescued" mutant heart tube. In this study, to get a more highly purified sample of the "active" molecule, RNA extracted from endoderm-conditioned medium and was assayed for its ability to promote myofibrillogenesis in mutant hearts. Mutant heart mesoderm responded to conditioned-medium RNA in a dose-dependent manner. Proteinase K treatment of the RNA did not affect inductive activity, while digestion with RNase A completely abolished the ability to rescue mutant hearts. Confocal laser scanning microscopy of immunostained, organ-cultured hearts revealed that mutant hearts contain reduced amounts of the sarcomeric protein tropomyosin in an amorphous distribution, whereas normal and corrected mutant hearts contain tropomyosin primarily in organized myofibrils.
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PMID:RNA from normal anterior endoderm/mesoderm-conditioned medium stimulates myofibrillogenesis in developing mutant axolotl hearts. 751 83

Expression of several muscle-specific genes was monitored during chicken muscle development and myoblast differentiation in primary cultures. The individual patterns of expression for many muscle-specific genes are well documented in ovo and in other model systems of muscle development. However, comparison of aldolase A to other muscle-specific genes in one system has not been reported. Both sarcomeric and cytosolic genes important for the adult muscle fiber were examined in order to elucidate their timing of expression and its relationship to cell fusion. Steady-state mRNA expression was measured using RNase protection assays with cRNA probes generated from cDNA clones for muscle creatine kinase, fast skeletal troponin-T, embryonic myosin heavy chain, and aldolase A. Nonmuscle genes expressed largely in the embryo, aldolase C and beta-actin, were used as controls. The expression of all six genes revealed differences in temporal expression patterns between limb and axial muscle. The temporal expression patterns of all six genes were also monitored in primary myoblast cultures relative to myoblast fusion. In both axial and limb myoblast cultures most of the muscle-specific genes were expressed prior to fusion. During the differentiation of myoblasts to myotubes there was a biphasic pattern in the expression of the muscle-specific genes. The appearance of measurable mRNA was detected by 16 hr in culture, prior to appreciable fusion of the cells. During further differentiation the expression increased gradually and then more rapidly at 96 hr, once fusion was complete. Meanwhile, the nonmuscle embryonic gene expression declined only slightly. For one gene, aldolase A, expression was delayed relative to the other muscle-specific genes, both in the appearance of measurable mRNA and in the later rapid increase in mRNA.
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PMID:Expression of aldolase A steady-state mRNA is delayed relative to other muscle-specific genes during differentiation of chicken myoblasts. 766 43

Peptide growth factors likely play an important role in cardiac development, but growth factors which inhibit or prevent differentiation in cardiac myocytes are largely unknown. Using immunocytochemistry, Western and Northern blotting, and RNase protection assays, we demonstrate that epidermal growth factor (EGF) significantly inhibits differentiation and promotes proliferation in cultured human fetal ventricular cardiac myocyte cell lines. In enriched cell lines and in a pure myocyte cell strain, EGF inhibited increases in immunoreactive sarcomeric actin and sarcomeric myosin heavy chain (SMHC) normally seen after serum withdrawal. In the pure myocyte strain, EGF induced a cardiomyoblastic phenotype; i.e., it caused a complete loss of detectable sarcomeric proteins in the majority of cells; it was also mitogenic. EGF inhibited expression of cardiac alpha-actin and SMHC mRNAs, but inhibition of SMHC expression was predominantly of the beta-MHC isoform. Removal of EGF was followed by reexpression of sarcomeric proteins. Blocking the EGF receptor (EGFR) with monoclonal anti-receptor antibody completely abolished the dedifferentiating effects of EGF and also significantly reduced the mitogenic effect of the peptide. The results indicate that activation of the EGFR both inhibits differentiation and promotes proliferation of human fetal ventricular myocytes in vitro. These findings suggest an important role for EGF in human cardiac differentiation and development.
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PMID:Epidermal growth factor promotes a cardiomyoblastic phenotype in human fetal cardiac myocytes. 891 16

Myogenesis proceeds by fusion of proliferating myoblasts into myotubes under the control of various transcription factors. In adult skeletal muscle, myogenic stem cells are represented by the satellite cells which can be cultured and differentiate in vitro. This system was used to investigate the subcellular distribution of a particular type of prosomes at different steps of the myogenic process. Prosomes constitute the MCP core of the 26S proteasomes but were first observed as subcomplexes of the untranslated mRNPs; recently, their RNase activity was discovered. A monoclonal antibody raised against the p27K subunit showed that the p27K subunit-specific prosomes move transiently into the nucleus prior to the onset of myoblast fusion into myotubes; this represents possibly one of the first signs of myoblast switching into the differentiation pathway. Prior to fusion, the prosomes containing the p27K subunit return to the cytoplasm, where they align with the gradually formed lengthwise-running desmin-type intermediate filaments and the microfilaments, co-localizing finally with the actin bundles. The prosomes progressively form discontinuous punctate structures which eventually develop a pseudo-sarcomeric banding pattern. In myotubes just formed in vitro, the formation of this pattern seems to preceed that produced by the muscle-specific sarcomeric (alpha)-actin. Interestingly, this pattern of prosomes of myotubes in terminal in vitro differentiation was very similar to that of prosomes observed in vivo in foetal and adult muscle. These observations are discussed in relation to molecular myogenesis and prosome/proteasome function.
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PMID:Dynamic distribution and formation of a para-sarcomeric banding pattern of prosomes during myogenic differentiation of satellite cells in vitro. 1019 81

Prosomes (20S proteasomes) constitute the catalytic core of the 26S proteasomes, but were first observed as factors associated with unstranslated mRNA. Recently, their RNase activity was discovered together with the fact that their proteolytic function is dispensable in adapted human cells. By indirect immunofluorescence using monoclonal antibodies, we demonstrate as a general phenomenon, regular intercalation of specific types of prosomes into the sarcomeric structure of all types of striated muscle. Surprisingly, in cultured smooth muscle cells without sarcomeric organization, some prosomes also form regular striations in extended projections of cytoplasmic regions. The significance of their sarcomeric distribution is not understood as yet, but the pattern we observe is very similar to that shown by others for muscle-specific mRNAs, identified by in situ hybridization, and that of the cognate proteins. A role of prosomes in the cotranslational assembly of the myofibrillar proteins is suggested, since prosomes organize into pseudo-sarcomeric patterns prior to formation de novo of the actin-myosin arrangement.
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PMID:Prosomes form sarcomere-like banding patterns in skeletal, cardiac, and smooth muscle cells. 1133 38