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)

When the action of highly purified specimens of ribonuclease H (hybrid nuclease; RNA-DNA hybrid ribonucleotidohydrolase; EC 3.1.4.34) of calf thymus on a wide selection of homopolymer hybrids was studied, the extent, and even the occurrence, of hydrolysis was found to be governed by the interplay of several factors: the composition of the ribo strand, the length of the deoxyribo strand, and the nature of the activating metal. Mn2+ activates the enzymic cleavage of all hybrid combinations, Mg2+ only of those containing purine ribo strands, Co2+ only of poly(A) hybrids. A 1:1 hybrid of phage f1 DNA and RNA is, however, split in the presence of any of these activators. Hybrids with deoxyribo tetranucleotides can still be cleaved, but not with dinucleotides. The behavior of hybrids containing covalently linked runs of ribo and deoxyribopolynucleotides was studied with the hybrid poly(dT)-poly(A)7-(dA)X]. This hybrid is attacked by ribonuclease H so that the bulk of the resulting poly(dA) still retains one covalently linked riboadenylic acid end group, whereas a small proportion carries a ribo dinucleotide. Inhibition studies showed that ribonuclease H is inactivated irreversibly by pretreatment with S-adenosylmethionine at 35 degrees, but not at 0 degrees. S-Adenosylhomocysteine also is inhibitory, but not irreversibly; also it is essentially limited to the inhibition of the cleavage of purine ribo strands. When the enzyme is exposed simultaneously to both inhibitors, irreversible inactivation is diminished considerably.
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PMID:Ribonuclease H of calf thymus: substrate specificity, activation, inhibition. 106 91

A 1.67-kb segment of the equine infectious anemia virus pol gene, encoding a 66-kDa reverse transcriptase (RT), was cloned and expressed in Escherichia coli. Recombinant RT, purified by a combination of metal chelate affinity chromatography and ion-exchange chromatography, displays both RNA-dependent DNA polymerase and RNase H activity. The affinity of purified RT for its replication primer, tRNA(3Lys) was equivalent to that observed for human immunodeficiency virus RT. Our data suggest that an additional domain between RT-RNase H and integrase on the equine infectious anemia virus pol open reading frame is not an integral component of the RT polypeptide.
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PMID:Purification and characterization of recombinant equine infectious anemia virus reverse transcriptase. 171 38

A 1.6-kilobase-pair DNA fragment derived from the Escherichia coli chromosome was analyzed by Tn3 transposon insertion and deletion mapping to locate a mutator gene, dnaQ (mutD), and the rnh gene that codes for RNase H. When a strong promoter, PL of lambda phage, was placed at the right- and left-side of the cloned DNA fragment, the dnaQ protein and RNase H, respectively were overproduced. These results suggested that the two genes are transcribed in opposite directions and that their promoters are located in a narrow region between the genes. Nucleotide sequence analysis confirmed this and further revealed that transcriptional and translational initiation signals for the two genes overlap. From the sequence data it was deduced that the dnaQ protein and RNase H consist of 243 and 155 triplets and have molecular weights of 27,500 and 17,500, respectively. dnaQ81 amber mutant showed two codon alterations, CAG(glutamine-195) leads to TAG(amber) and ACA(threonine-193) leads to ATA(isoleucine). The dnaQ-lacZ and the rnh-lacZ fused genes were constructed and hybrid proteins with beta-galactosidase activity were produced. From beta-galactosidase levels it was estimated that the promoter for dnaQ is 5 times more active than that for rnh.
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PMID:Structure and expression of the dnaQ mutator and the RNase H genes of Escherichia coli: overlap of the promoter regions. 631 47

A 1 kb EcoRI restriction fragment cloned from a band visible in an agarose gel of Pinus lambertiana (sugar pine) genomic DNA is present in both subgenera of Pinus with at least 10(4) copies/genome. A full-length copy of this repeated element recovered from a P. radiata (Monterey pine) genomic DNA library was found to possess all of the sequence features associated with gypsy-like retrotransposons. This report describes the biology and history of the IFG (Institute of Forest Genetics) family of retrotransposons. The characterized IFG7 is 5937 bp long. Immediately interior to its 5' and 3' long terminal repeats are sequences consistent with primer binding sites for reverse transcription of the RNA genome. Presumptive gene products associated with retrotransposition appear to be coded in a single reading frame and are in the same order as the gypsy-like retrotransposons and retroviruses. The 1.0 kb EcoRI fragment of IFG elements codes for the 3' half of IFG's reverse transcriptase and the entire RNase H domain. Southern blot analysis suggests IFG was present in Pinaceae before its division into its modern genera. Sequence analysis of IFG 1.0 kb RI fragments and southern analysis also suggest that IFG continued to evolve in Pinus with restriction fragment length polymorphism (RFLP) subfamilies appearing early in the history of each subgenus often correlating with subdivisions of Pinus. Features shared with other plant retrotransposons are also discussed.
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PMID:IFG, a gypsy-like retrotransposon in Pinus (Pinaceae), has an extensive history in pines. 1009 71