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

We cloned the Saccharomyces cerevisiae homologue of mammalian RNase HI, which itself is related to the prokaryotic RNase HII, an enzyme of unknown function and previously described as having minor activity in Escherichia coli. Expression of the corresponding yeast 35 kDa protein (named by us RNase H(35)) in E. coli and immunological analysis proves a close evolutionary relationship to mammalian RNase HI. Deletion of the gene (called RNH35) from the yeast genome leads to an about 75% decrease of RNase H activity in preparations from the mutated, still viable cells. Sequence comparison discriminates this new yeast RNase H from earlier described yeast enzymes, RNase H(70) and RNase HI.
 ...
PMID:Yeast RNase H(35) is the counterpart of the mammalian RNase HI, and is evolutionarily related to prokaryotic RNase HII. 946 32

Two RNases H of mammalian tissues have been described: RNase HI, the activity of which was found to rise during DNA replication, and RNase HII, which may be involved in transcription. RNase HI is the major mammalian enzyme representing around 85% of the total RNase H activity in the cell. By using highly purified calf thymus RNase HI we identified the sequences of several tryptic peptides. This information enabled us to determine the sequence of the cDNA coding for the large subunit of human RNase HI. The corresponding ORF of 897 nt defines a polypeptide of relative molecular mass of 33,367, which is in agreement with the molecular mass obtained earlier by SDS/PAGE. Expression of the cloned ORF in Escherichia coli leads to a polypeptide, which is specifically recognized by an antiserum raised against calf thymus RNase HI. Interestingly, the deduced amino acid sequence of this subunit of human RNase HI displays significant homology to RNase HII from E. coli, an enzyme of unknown function and previously judged as a minor activity. This finding suggests an evolutionary link between the mammalian RNases HI and the prokaryotic RNases HII. The idea of a mammalian RNase HI large subunit being a strongly conserved protein is substantiated by the existence of homologous ORFs in the genomes of other eukaryotes and of all eubacteria and archaebacteria that have been completely sequenced.
 ...
PMID:Cloning of the cDNA encoding the large subunit of human RNase HI, a homologue of the prokaryotic RNase HII. 978 7

Correct removal of RNA primers of Okazaki fragments during lagging-strand DNA synthesis is a critical process for the maintenance of genome integrity. Disturbance of this process has severe mutagenic consequences and could contribute to the development of cancer. The role of the mammalian nucleases RNase HI and FEN-1 in RNA primer removal has been substantiated by several studies. Recently, RNase H(35), the Saccharomyces cerevisiae homologue of mammalian RNase HI, was identified and its possible role in DNA replication was proposed (P. Frank, C. Braunshofer-Reiter, and U. Wintersberger, FEBS Lett. 421:23-26, 1998). This led to the possibility of moving to the genetically powerful yeast system for studying the homologues of RNase HI and FEN-1, i.e., RNase H(35) and Rad27p, respectively. In this study, we have biochemically defined the substrate specificities and the cooperative as well as independent cleavage mechanisms of S. cerevisiae RNase H(35) and Rad27 nuclease by using Okazaki fragment model substrates. We have also determined the additive and compensatory pathological effects of gene deletion and overexpression of these two enzymes. Furthermore, the mutagenic consequences of the nuclease deficiencies have been analyzed. Based on our findings, we suggest that three alternative RNA primer removal pathways of different efficiencies involve RNase H(35) and Rad27 nucleases in yeast.
 ...
PMID:Saccharomyces cerevisiae RNase H(35) functions in RNA primer removal during lagging-strand DNA synthesis, most efficiently in cooperation with Rad27 nuclease. 1056 61