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

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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)

Lysine vasopressin- and oxytocin-encoding mRNAs have been analysed in the developing hypothalamus of the pig. The two hormone-encoding mRNAs were first detectable on fetal day 49 by Northern blot analysis. Whereas RNase mapping revealed identical transcripts throughout the developmental stages studied, Northern blots showed that the early transcripts appeared to be shorter (by 100-200 nucleotides) and more heterogeneous in size than those of later stages. This developmentally related length polymorphism was shown to be due to different poly(A) lengths and was abolished by removal of the poly(A) tails with RNase H. These results indicate that maturation of neurones in the developing porcine hypothalamus is accompanied by an increase in length of the poly(A) tail of vasopressin and oxytocin mRNAs.
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PMID:Poly(A) tail length of oxytocin- and lysine vasopressin-encoding mRNAs increases during development in the porcine hypothalamus. 197 13

An additional RNase H (EC 3.1.26.4), RNase HII, has been isolated from Escherichia coli K-12. By screening a library of E. coli DNA for clones that suppressed RNase H deficiency of an E. coli rnh mutant, a clone was obtained that produced a protein with RNase H activity. The overexpressed RNase HIII protein in E. coli was purified to near homogeneity and exhibited a strong preference for the ribonucleotide moiety of RNA-DNA hybrid as substrate. The terminal 11 amino acids were determined and were identical to those predicted from the nucleotide sequence. The rnhB gene, which encodes RNase HII, was distinct from rnhA by its map position (4.5 min on E. coli genetic map, between lpxB and dnaE) and by the lack of significant amino acid sequence similarity. The presence of a second RNase H in E. coli indicates that multiple RNase H genes per genome is a general feature of a general feature of a wide variety of organisms.
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PMID:Isolation and characterization of a second RNase H (RNase HII) of Escherichia coli K-12 encoded by the rnhB gene. 217 91

Oligoribonucleotide duplexes containing one to four 2'-deoxynucleotide residues were used as substrates for ribonuclease V1 and RNase H. Either deoxyadenosine and/or deoxythymidine were incorporated into the duplex, 5'GGCCGGAUCCGCGC3'-5'GCGCGGAUCCGGCC3' by substitution of the appropriate deoxynucleoside triphosphate into a transcription reaction with T7 RNA polymerase. The melting temperature, Tm, of the duplex (1.8 microM in strands in 50 mM NaCl) containing only ribonucleotides was 79.9 degrees C. Substitution of deoxyadenosine in both strands of the duplex lowered the Tm by 2.4 degrees C. Substitution of deoxythymidine had no measurable effect on the Tm. Comparison of RNase V1 digestion patterns of fully ribonucleotide and deoxy-substituted duplexes suggest that any distortion is localized to the site of the substitution. An oligoribonucleotide containing two deoxy residues directs specific cleavage of RNA by E. coli RNase H. Structural requirements for cleavage are proposed for RNase V1 and RNase H.
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PMID:Deoxynucleotide-containing oligoribonucleotide duplexes: stability and susceptibility to RNase V1 and RNase H. 255 16

Previous studies have revealed multiple size classes of rat insulin-like growth factor-I (IGF-I) of estimated size 7.5-7.0, 1.9-1.5, and 1.2-0.9 kilobases (kb). Available sequence information accounts for only 2.1 kb of the 7.5-7.0 kb IGF-I mRNAs. We used oligomer directed ribonuclease H (RNase H) mapping to define the extent to which the unknown sequence in the large molecular weight mRNAs lies 5' or 3' to known sequence. Rat liver polyadenylated RNAs were incubated with oligomer probes complementary to internal rat IGF-I precursor (E domain) coding sequences. RNase H was used to hydrolyze IGF-I mRNAs at the point of annealment with the oligomers. Resultant 5' and 3'-IGF-I mRNA fragments were analyzed on Northern blots. A probe specific for type 1 (class C) 5'-sequences (the most predominant of multiple 5'-sequence types found on rat IGF-I mRNAs) identifies intact IGF-I mRNAs of 7.5-7.0, 1.9-1.5 and 1.2-0.9 kb but, after oligomer directed RNase cleavage of these mRNAs, identified only a single IGF-I mRNA 5'-fragment. Major differences in the length of sequence 5' to the IGF-I coding sequence therefore, do not account for the multiple size classes of type 1 (class C) IGF-I mRNAs. The size of the 5'-fragment suggests that the extent of sequence 5' to the IGF-I coding sequence is 0.4-0.7 kb in type 1 (class C) IGF-I mRNAs. Identification of multiple 3'-fragments of IGF-I mRNAs demonstrated heterogeneity in the 3'-ends of rat IGF-I mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The size heterogeneity of rat insulin-like growth factor-I mRNAs is due primarily to differences in the length of 3'-untranslated sequence. 256 Aug 8

I have previously reported an activity in HeLa cells which facilitates transcript displacement by purified mammalian RNA polymerase II in vitro. I have shown that this activity copurifies with one of two separable ribonuclease (RNase) H activities in HeLa cells. The RNase H activity in question has characteristics similar to those reported for RNase H2b from calf thymus. RNase H proteins purified from several other sources including Escherichia coli also show renaturase activity. When the renaturase/RNase H protein is present during transcription by purified RNA polymerase II, transcripts are truncated close to the 5' end, and the remainder of the transcript is displaced normally from its template by the polymerase. Since RNA polymerase II dependent transcripts in vivo normally require the presence of the 5'-triphosphate terminus for capping, the in vivo significance of RNase H as a renaturase factor is presently not understood. However, the in vitro action of renaturase/RNase H suggests that the mechanism of this reaction may involve R-loop displacement after formation of a short single-stranded region of DNA on the template strand following hydrolysis of a hybrid transcript oligonucleotide by RNase H.
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PMID:Renaturase and ribonuclease H: a novel mechanism that influences transcript displacement by RNA polymerase II in vitro. 283 25

The POMC gene is predominantly expressed in the pituitary gland; it is also expressed in various extrapituitary tissues. While POMC mRNAs of similar size (approximately equal to 1000 nucleotides) are present in the anterior and neurointermediate lobes of the pituitary, other POMC-expressing tissues contain POMC mRNAs of different sizes. Longer POMC mRNAs are observed in the hypothalamus. Using S1 nuclease mapping and mRNA deadenylation by RNase H, we have shown that these large hypothalamic POMC mRNAs have longer poly(A) tails than pituitary POMC transcripts but contain the same transcripted sequences. In contrast, the testes contain POMC transcripts which are smaller than pituitary POMC mRNA. RNase and S1 nuclease mapping analyses suggest that these short transcripts do not contain sequences transcribed from pituitary exons 1 and 2. Indeed, as revealed by primer-extension experiments, these transcripts appear to initiate within exon 3 sequences of the POMC gene. The heterogeneous 5'-ends of these short testicular transcripts map into the NH2-terminal portion of the precursor in the region encoding gamma MSH; if ever translated, these transcripts would produce a form of POMC that would be truncated at the NH2-terminus and therefore would be devoid of any signal peptide sequence. Interestingly, the sequence of the short testicular transcripts corresponds to that of the mouse POMC pseudogene, suggesting that this POMC pseudogene may have derived from genomic integration of testicular transcripts via a cDNA intermediate.
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PMID:Unusual proopiomelanocortin ribonucleic acids in extrapituitary tissues: intronless transcripts in testes and long poly(A) tails in hypothalamus. 285 1

A method for assaying hybrid ribonuclease has been devised which utilizes as substrate the synthetic hybrid [3H]polyriboadenylic acid [poly(rA)]:polydeoxythymidylic acid [poly(dT)] immobilized on the solid matrix of nitrocellulose filters. The hybridization on filter of [3H]poly(rA) to poly(dT) has been explored in terms of efficacy of the process and the response of the product to RNase H. A pulse of uv irradiation of poly(dT) while in dry state on the filter increased its firm binding to the filter in a concentration-dependent manner, resulting in a concomitant increase of the yield of hybrid formation. The filter-immobilized hybrid was 95% resistant to RNase A but sensitive to RNase H. When stored in toluene in the cold the hybrid maintained its stability for over 6 months, as judged by its resistance to RNase A. The method offers a number of advantages over assays that use solution hybrids as substrates and was readily applicable in the screening of leukemic patients, in the leukocytes of which it has demonstrated increased RNase H levels.
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PMID:Assay of hybrid ribonuclease using a membrane filter-immobilized synthetic hybrid: application to the human leukemic cell. 298 68

An RNase A protection assay was employed to investigate the interaction of nuclear components with a precursor-mRNA derived from the adenovirus 2 major late transcription unit in a splicing extract from HeLa cells. Upon incubation in the extract, two regions in the precursor-RNA become resistant to digestion with RNase A. After short incubation times (5 min) at 30 degrees C, fragments mapping upstream from the branch point in the intron are obtained. After ten minutes or more, additional oligonucleotides, derived from the 5' splice site, are protected. RNase A protection of different RNA substrates demonstrates that a 5' splice site is not required for the binding of components to the branch point region. For interaction with this site, the polypyrimidine stretch just upstream from the 3' splice site is essential. Binding to the 5' splice site occurs only in the presence of an intact 3' end of the intron. Preincubation of the extract with excess unlabelled RNA containing only a 3' splice site leads to efficient competition of binding, both in the branch point region and at the 5' splice site, whereas an RNA that contains only 5'-splice-site sequences has no effect on the interaction with the mRNA precursor. This indicates that stable association with the 5' splice site requires prior binding of components in the branch point region. When splicing complexes are digested with RNase A, it becomes apparent that only the branch point region is sequestered into a ribonucleoprotein (RNP) structure in the 35 S complex. The 5' splice site becomes resistant to RNase A only when a 50 S splicing complex has been assembled. Degradation of specific regions in U1, U2 and U4 RNA with complementary oligodeoxynucleotides and RNase H has been used to analyse involvement of the U small nuclear RNPs (snRNPs) in the protection reaction. The 5' end of U2 RNA is essential for protection of the branch point region. RNA sequences in a loop of U2 RNA (nucleotides 65 to 78) are required for the formation of an RNase-A-resistant structure at the 5' splice site. Taken together, these results suggest that U2 snRNP participates in the formation of a pre-splicing complex, the 5' end of its RNA being involved in the observed binding. Conversion to a 50 S splicing complex is obtained after the binding of U1 and U4/U6 snRNPs, which also requires sequences in a loop of U2 RNA. Possible interactions between the individual snRNPs and between snRNPs and precursor-mRNA are discussed.
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PMID:Analysis of RNase-A-resistant regions of adenovirus 2 major late precursor-mRNA in splicing extracts reveals an ordered interaction of nuclear components with the substrate RNA. 368 67

The poly(A) sequence of 30 to 40S Rous sarcoma virus RNA, prepared by digestion of the RNA with RNase T(1), showed a rather homogenous electrophoretic distribution in formamide-polyacrylamide gels. Its size was estimated to be about 200 AMP residues. The poly(A) appears to be located at or near the 3' end of the 30 to 40S RNA because: (i) it contained one adenosine per 180 AMP residues, and because (ii) incubation of 30 to 40S RNA with bacterial RNase H in the presence of poly(dT) removed its poly(A) without significantly affecting its hydrodynamic or electrophoretic properties in denaturing solvents. The viral 60 to 70S RNA complex was found to consist of 30 to 40S subunits both with (65%) and without (approximately 30%) poly(A). The heteropolymeric sequences of these two species of 30 to 40S subunits have the same RNase T(1)-resistant oligonucleotide composition. Some, perhaps all, RNase T(1)-resistant oligonucleotides of 30 to 40S Rous sarcoma virus RNA appear to have a unique location relative to the poly(A) sequence, because the complexity of poly(A)-tagged fragments of 30 to 40S RNA decreased with decreasing size of the fragment. Two RNase T(1)-resistant oligonucleotides which distinguish sarcoma virus Prague B RNA from that of a transformation-defective deletion mutant of the same virus appear to be associated with an 11S poly(A)-tagged fragment of Prague B RNA. Thus RNA sequences concerned with cell transformation seem to be located within 5 to 10% of the 3' terminus of Prague B RNA.
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PMID:Properties and location of poly(A) in Rous sarcoma virus RNA. 437 9

The synthesis of the covalently-closed, circular DNA form of colicinogenic factor E(1) (ColE(1)) continues in Escherichia coli cells after the addition of chloramphenicol. A large portion of the purified supercoiled ColE(1) DNA molecules made in the presence of chloramphenicol are converted to the open circular DNA form after treatment with alkali (pH 13), RNase A, or RNase H. These treatments do not significantly affect the covalently-closed form of ColE(1) DNA isolated from normally growing E. coli cells. The open circular product resulting from treatment of supercoiled ColE(1) DNA with RNase A possesses a single break in one strand of the circular duplex. The site sensitive to RNase A occurs with equal probability in either of the complementary strands. Both synthesis of ColE(1) DNA and the formation of supercoiled ColE(1) DNA sensitive to RNase A or alkali are prevented by the inhibitor of RNA synthesis, rifampicin. These results indicate that covalently-closed ColE(1) DNA containing one or more ribonucleotides accumulates during ColE(1) replication in the presence of chloramphenicol. It is proposed that this incorporated RNA served as a primer during the initiation of synthesis of ColE(1) DNA and that its removal from the circular DNA is inhibited in cells incubated in the presence of chloramphenicol.
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PMID:Isolation of supercoiled colicinogenic factor E 1 DNA sensitive to ribonuclease and alkali. 456 Jun 90


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