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Results for “RNase HII”

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4 recordsLinked to original sources

PubMed2026

Bacillus subtilis RNase HII Is Inefficient at Processing Guanosine Monophosphate and Damaged Ribonucleotides.

During one round of DNA replication, nearly 2000 ribonucleoside monophosphates (rNMPs) are incorporated in place of their cognate deoxyribonucleoside monophosphates (dNMPs). Given their high rate of insertion, genomic DNA could contain rNMPs that are damaged or mismatched. Here, we test the activity of Bacillus subtilis and Escherichia coli RNase HII on canonical, mismatched, and damaged rNMPs. We show that E. coli RNase HII is adept at incising most rNMP variants from DNA at similar frequencies, with the exception of an oxidized rNMP, where endoribonuclease activity is sharply reduced. In contrast, B. subtilis RNase HII efficiently incises rAMP, rCMP, and rUMP but is inefficient at processing rGMP in both a canonical and mismatched base pair. We test damaged ribonucleotides and find that B. subtilis RNase HII is refractory to processing abasic and oxidized ribonucleotide lesions. Our work shows that bacterial RNase HII enzymes have different intrinsic endoribonuclease activity toward the repair of canonical, mismatched, and damaged rNMPs, demonstrating that not all rNMP errors provoke efficient resolution. Our finding that B. subtilis RNase HII is recalcitrant to repairing damaged rNMPs resembles what is observed for eukaryotic RNase H2 orthologs, suggesting that other repair processes are necessary to resolve damaged rNMPs.

Bacillus subtilis↗

PubMed2025

Bacillus subtilis RNase HII is inefficient at processing guanosine monophosphate and damaged ribonucleotides.

During one round of DNA replication, nearly 2,000 ribonucleoside monophosphates (rNMPs) are incorporated in place of their cognate deoxyribonucleoside monophosphate (dNMP). Given their high rate of insertion, genomic DNA would contain rNMPs that are damaged or mismatched. Here, we tested the activity of Bacillus subtilis and Escherichia coli RNase HII on all four canonical, mismatched, and damaged rNMPs. We show that E. coli RNase HII is adept at incising most rNMP variants from DNA at similar frequencies, with the exception of an oxidized rNMP, where endoribonuclease activity is sharply reduced. In contrast, B. subtilis RNase HII efficiently incised rAMP, rCMP, and rUMP, but was inefficient at processing rGMP in both a canonical and mismatched base pair. We tested damaged ribonucleotides and found that B. subtilis RNase HII is refractory to processing abasic and oxidized ribonucleotide lesions. Our work shows that bacterial RNase HII enzymes have different intrinsic endoribonuclease activity toward the repair of canonical, mismatched, and damaged rNMPs, demonstrating that not all rNMP errors provoke efficient resolution. Our finding that B. subtilis RNase HII is recalcitrant to repairing damaged rNMPs resembles what is observed for eukaryotic RNase H2 orthologs, suggesting that other repair processes are necessary to resolve damaged rNMPs.

Bacillus subtilis↗

PubMed1990

Isolation and characterization of a second RNase H (RNase HII) of Escherichia coli K-12 encoded by the rnhB gene.

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.

Amino Acid Sequence↗

PubMed1991

Molecular cloning of a ribonuclease H (RNase HI) gene from an extreme thermophile Thermus thermophilus HB8: a thermostable RNase H can functionally replace the Escherichia coli enzyme in vivo.

A DNA fragment encoding Ribonuclease H (EC 3. 1.26.4) was isolated from an extreme thermophilic bacterium, Thermus thermophilus HB8, by its ability to complement the temperature-sensitive growth of an Escherichia coli rnhA deficient mutant. The primary amino acid sequence showed 56% similarity to that of E. coli RNase HI but little or no homology to E. coli RNase HII. Enzymes derived from thermophilic organisms tend to have fewer cysteines than their bacterial counterparts. However, T. thermophilus RNase H has one more cysteine than its E. coli homologue. Stability of the RNase H in extracts of T. thermophilus to elevated temperatures was the same for the protein expressed in E. coli. T. thermophilus RNase H should, therefore, be a useful tool for editing RNA-DNA hybrid molecules at higher temperatures and may also be stable enough to be used in a cyclical process. It was suggested that regulation of expression of the RNase H may be different from that of E. coli. RNase HI.

Amino Acid Sequence↗