Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ribosomes play an active role in protein biosynthesis. Ribosomal RNA conformation in ribosomal subunits, intramolecular interactions between different rRNA sequences within the confinement of the particles, and intermolecular interactions are presumed necessary to support efficient and accurate protein synthesis. Here we report an analysis of the disposition of 16S rRNA conserved zones centered about positions 525, 1400, and 1500 in 30S subunits. Complementary oligodeoxyribonucleotides in conjunction with nuclease S1 digestion were used to do this. All of the sequences examined in 30S subunits are accessible to DNA probes of 9 to 12 nucleotide residues in length. However, the kinetic characteristics of the respective DNA interactions with 30S particles vary significantly. In addition to the investigation of normal 30S particles, a four base deletion within the 1400 region of 16S rRNA was analyzed. The deletion was made by using synthetic DNAs to target the deletion site for RNase H digestion. The direct in vitro procedure for manipulating rRNA conserves nucleotide modifications. The alteration causes a significant change in the disposition of 16S rRNA in 30S subunits, suggesting a reduction in the freedom of movement of the altered zone in the particle. In a factor-dependent in vitro protein synthesis system primed with MS2 mRNA and altered 30S subunits, there was a 50% decrease in phage coat protein synthesis. The reduction could be due to a decrease in the rate of translation or premature termination of translation. We present evidence here, based on isotopic studies, which supports the latter possibility.
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PMID:Probing the function of conserved RNA structures in the 30S subunit of Escherichia coli ribosomes. 166 66

RNase H has been used for selective cleavage of RNA of MS2 and R17 bacteriophages and 16S RNA from E. coli ribosomes in the region of formation of heteroduplex composed of RNA and an oligodeoxyribonucleotide complementary to a certain part of it. The oligonucleotides used--d(C-T-C-A-T-G-T-T-), d(C-C-A-T-C-T-T-T-T) and d(T-T-T-C-C-A-T-C-T-T-T-T)--were synthesized by chemical methods. The molecular weight of the fragments produced on cleavage of the RNA of MS2 and R17 were estimated with the use of gel electrophoresis under denaturating conditions. The dependence of the enzyme activity on Mg2+ and Na+ concentration and of RNA cleavage on the RNA: oligodeoxyribonucleotide ratio was investigated.
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PMID:[Addressed enzymatic fragmentation of RNA molecules]. 626 32

We describe characterization of spliceosomes affinity purified under native conditions. These spliceosomes consist largely of C complex containing splicing intermediates. After C complex assembly on an MS2 affinity-tagged pre-mRNA substrate containing a 3' splice site mutation, followed by RNase H digestion of earlier complexes, spliceosomes were purified by size exclusion and affinity selection. This protocol yielded 40S C complexes in sufficient quantities to visualize in negative stain by electron microscopy. Complexes purified in this way contain U2, U5, and U6 snRNAs, but very little U1 or U4 snRNA. Analysis by tandem mass spectrometry confirmed the presence of core snRNP proteins (SM and LSM), U2 and U5 snRNP-specific proteins, and the second step factors Prp16, Prp17, Slu7, and Prp22. In contrast, proteins specific to earlier splicing complexes, such as U2AF and U1 snRNP components, were not detected in C complex, but were present in similarly purified H complex. Images of these spliceosomes revealed single particles with dimensions of approximately 270 x 240 A that assort into well-defined classes. These images represent an important first step toward attaining a comprehensive three-dimensional understanding of pre-mRNA splicing.
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PMID:Purification and characterization of native spliceosomes suitable for three-dimensional structural analysis. 1199 38

A series of DNA-linked RNases H, in which the 15-mer DNA is cross-linked to the Thermus thermophilus RNase HI (TRNH) variants at positions 135, 136, 137 and 138, were constructed and analyzed for their abilities to cleave the complementary 15-mer RNA. Of these, that with the DNA adduct at position 135 most efficiently cleaved the RNA substrate, indicating that position 135 is the most appropriate cross-linking site among those examined. To examine whether DNA-linked RNase H also site-specifically cleaves a highly structured natural RNA, DNA-linked TRNHs with a series of DNA adducts varying in size at position 135 were constructed and analyzed for their abilities to cleave MS2 RNA. These DNA adducts were designed such that DNA-linked enzymes cleave MS2 RNA at a loop around residue 2790. Of the four DNA-linked TRNHs with the 8-, 12-, 16- and 20-mer DNA adducts, only that with the 16-mer DNA adduct efficiently and site-specifically cleaved MS2 RNA. Primer extension revealed that this DNA-linked TRNH cleaved MS2 RNA within the target sequence.
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PMID:Site-specific cleavage of MS2 RNA by a thermostable DNA-linked RNase H. 1236 83