Disease relevance of Rnaseh1

• Sequence alignments indicate that MLV Y586 is equivalent to HIV-1 Y501, a component of the recently described RNase H primer grip domain, which contacts and positions the DNA primer strand near the RNase H active site [1].
• As compared to the attenuated virus from cultures of 5-86 and G-2 cells, the subunits of the RNA from the virions of SQ-A cells are the same size, and the amount of reverse transcriptase activity and RNase H present in the purified virions of the three lines are similar [2].
• The reverse transcriptase enzymes of retroviruses are multifunctional proteins containing both DNA polymerase activity and a nuclease activity, termed RNase H, specific for RNA in RNA-DNA hybrid form [3].
• Escherichia coli RNase H has a basic extension that is involved in binding nucleic acid substrates [4].
• This basic extension is present in the RNase H of Moloney murine leukemia virus reverse transcriptase (MLV RT), but has been deleted from the RNase H of HIV-1 RT [4].

High impact information on Rnaseh1

• As expected, oligo-nucleotide-directed RNase H cleavage of this portion of murine U7 inhibits the in vitro processing reaction [5].
• These findings indicate that the RNase H primer grip can affect the template-primer conformation at the polymerase active site and that the MLV Y586 residue and template-primer conformation are important determinants of RT fidelity [1].
• The relative contributions of polymerase-dependent and polymerase-independent RNase H activities during reverse transcription and template switching in vivo have not been determined [6].
• Dynamic copy choice: steady state between murine leukemia virus polymerase and polymerase-dependent RNase H activity determines frequency of in vivo template switching [6].
• Because only polymerase-independent RNase H activity is present in this cell line, the relative roles of polymerase-dependent and -independent RNase H activities in template switching could be determined [6].

Biological context of Rnaseh1

• In mitochondria, where RNase H1 is essential for DNA formation during embryogenesis, long hybrids may be involved in DNA replication [7].
• RNase H analysis demonstrates that this migration change was due to an increase in mRNA polyadenylation [8].
• To determine the role of RNase H activity in retroviral replication, we constructed a series of mutant genomes of Moloney murine leukemia virus that encoded reverse transcriptase enzymes that were specifically altered to retain polymerase function but lack RNase H activity [3].
• These results suggest that RNase H normally promotes strong-stop translocation, perhaps by exposing single-stranded DNA sequences for base pairing [3].
• Antisense oligonucleotides (ONs) are designed to hybridize target mRNA in a sequence-specific manner and inhibit gene expression by preventing translation, either by activation of RNase H or steric blockage of the ribosome complex [9].

Anatomical context of Rnaseh1

• Freshly prepared reticulocyte lysates were found to contain 1-2% of the level of RNase H in nucleated cells [10].
• The relative roles of these three types of Na+/Pi co-transporters in Pi transport in mouse kidney cortex have now been investigated by RNase H-mediated hybrid depletion [11].
• When poly(A) tracts were selectively removed from germ cell RNAs by ribonuclease H treatment, identical 1.3-kb CD-MPR mRNAs were detected in pachytene spermatocytes and round spermatids, indicating that the size difference between the 1.4- and 1.6-kb transcripts is due to variations in poly(A) tail length.(ABSTRACT TRUNCATED AT 250 WORDS)[12]
• Using the mFold program, we designed seven anti-pCD ribozymes and checked the accessibility to target pCD mRNA by RNase H cleavage experiment in a cell-free system [13].
• Hybridized RNA is then detected by incubation of membranes with Escherichia coli RNase H and DNA polymerase I. RNase H is used for nicking the RNA in the hybrids [14].

Associations of Rnaseh1 with chemical compounds

• Additionally, trans-complementation of RNase H mutants in the presence and absence of hydroxyurea, which slows the rate of reverse transcription, showed that hydroxyurea increased template switching only when polymerase-dependent RNase H activity was present [6].
• Thus an RNase H-dependent phosphorothioate oligodeoxynucleotide can be modified as a 2'-O-propyl 'chimeric' oligonucleotide to provide a significant increase in antisense activity in cell culture [15].
• The resulting RNase H-mediated cleavages in the cell extracts were quantified using RT-PCR with fluorescein and rhodaminetagged primers to generate fluorescent products that are analyzed and quantified on an automated DNA sequencer [16].
• Differential inhibition of DNA polymerase and RNase H activities of the reverse transcriptase by phosphonoformate [17].
• Only antisense ONs acting via an RNase H mechanism or by steric hindrance through covalent attachment (via transplatin modification) to the target mRNA were found to definitively arrest translation in this study [9].

Enzymatic interactions of Rnaseh1

• An ODN binding site in native MTase mRNA was identified that was cleaved by endogenous RNase H with an efficiency of 85% in the extracts [16].

Regulatory relationships of Rnaseh1

• Ribonuclease H analysis revealed that this T3-induced decrease in size was due to a shortening of poly(A) tail from approximately 160 to approximately 30 nucleotides and was specific for TSHbeta mRNA [18].

Other interactions of Rnaseh1

• RNase H analysis showed that the size difference between the two testicular Hoxa-4 transcripts of 1.35 and 1.45 kb was due to a postmeiotic increase in poly(A) tail length [19].
• The presence of RNase A, but not RNase H, inhibited exonucleolytic digestion, suggesting that a ribonucleoprotein is responsible for the exonucleolysis [20].
• The 16S RNA was annealed to globin cDNA and the hybrid digested with ribonuclease H. The undigested fragment did not bind to oligo(dT)-cellulose and its size was that expected for the intact 5' portion of the precursor [21].

Analytical, diagnostic and therapeutic context of Rnaseh1

• RNase H digestions and Northern blot analyses reveal that the three SOD-1 mRNAs are derived from two transcripts, a ubiquitously expressed transcript and a post-meiotic transcript, which differ by 114-120 nucleotides [22].
• Three methods were used to characterize the intron content of these pre-mRNA: Northern blot analysis, ribonuclease H mapping, and reverse transcription polymerase chain reaction analysis [23].
• Epitope mapping of HIV-1 reverse transcriptase with monoclonal antibodies that inhibit polymerase and RNase H activities [24].

References