enzyme form H2: requirement for divalent metal ion can be satisfied only by Mg2+. Enzyme form H1: requirement for a divalent metal ion can be satisfied by Mg2+ or with a stronger preference with Mn2+
translation initiates at each of the two in-frame AUGs of the Rnaseh1 mRNA, with the longer form being imported into mitochondria, subcellular localization study, overview
reverse transcriptase (RT) and ribonuclease H are among the most ancient and abundant protein folds. RNases H may have evolved from ribozymes, related to viroids, early in the RNA world, forming ribosomes, RNA replicases and polymerases. Basic RNA-binding peptides enhance ribozyme catalysis. RT and ribozymes or RNases H are present today in bacterial group II introns, the precedents of transposable elements. Thousands of unique RTs and RNases H are present in eukaryotes, bacteria, and viruses
mice deficient in RNase H1 that localizes to mitochondria die during embryogenesis, probably due to the defective processing of R-loops. RNase H2 knockout mice are also not viable, and mutations in either of the human genes can cause Aicardi-Goutieres Syndrome, a severe inheritable neurodevelopmental disorder. In this disease, uncleaved RNA-DNA hybrids accumulate within cells that possibly upregulate interferon via the nucleic acid sensor cyclic GMP-AMP synthase (cGAS) and its adaptor protein STING
the RNase H enzymes mediate viral and cellular replication and antiviral defense in eukaryotes and prokaryotes, splicing, R-loop resolvation, DNA repair. RNase H-like activities are also required for the activity of small regulatory RNAs. Virtually all known immune defense mechanisms against viruses, phages, transposable elements, and extracellular pathogens require RNase H-like enzymes. RNase H-like activities of retroviruses, transposable elements, and phages, have built up innate and adaptive immune systems throughout all domains of life. R-loops are formed when an RNA strand intercalates into dsDNA, resulting in RNA-DNA hybrids and single-stranded DNA loops. R-loops affect promoter activities, with a role in gene expression (e.g. of the c-Myc proto-oncogene), genome stability, CRISPR-Cas immunity, DNA repair, and cancer formation. RNases H can remove the RNA moiety and prevent deleterious DNA breaks
translation initiates at each of the two in-frame AUGs of the Rnaseh1 mRNA, with the longer form being imported into mitochondria, regulation mechanisms, modelling, overview
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
heterotrimeric complex of the RNase H2A, RNase H2B, and RNase H2C proteins, to 3.1 A resolution. The overall structure reveals an elongated arrangement of the subunits with the H2C protein in the middle flanked by the H2A and H2B proteins on the ends. Construction of a model for an Okazaki fragment binding to the mouse RNase H2 complex. In the model, the double-stranded RNA-DNA molecule runs through the active site cleft and is positioned to make several favorable electrostatic interactions and no significant steric clashes with the protein. The RNA-DNA hybrid is situated so that the target phosphodiester bond is in the proper orientation for nucleophile attack initiated by a two-metal ion chemistry
mutation in subunit H2A identified in patients with Aicardi-Goutieres' syndrome. Mutation appears to distort the active site accounting for the demonstrated substrate specificity modification
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CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
gene rnaseh1, translation initiates at each of the two in-frame AUGs of the Rnaseh1 mRNA, with the longer form being imported into mitochondria, regulation mechanisms, overview. Recombinant enzyme expression in Flp-In T-Rex-293 cells, and in vitro translation.