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)

Copper-zinc superoxide dismutase (SOD-1) is an enzyme that is widely expressed in eukaryotic cells and performs a vital role in protecting cells against free radical damage. In mouse testis, three different sizes of SOD-1 mRNAs of about 0.73, 0.80, and 0.93 kilobases (kb) are detected. The 0.73-kb mRNA is found in early stages of male germ cells and in all somatic tissues. The mRNAs of 0.80 and 0.93 kb are exclusively detected in post-meiotic germ cells. 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. RNase protection assays demonstrate that the additional nucleotides present in the post-meiotic mRNA are solely in the 5'-untranslated region. Using a probe derived from the 5'-untranslated region of the 0.93-kb SOD-1 mRNA, we have established that it originates from an alternative upstream promoter contiguous with the somatic SOD-1 promoter. Polysomal gradient analysis of the three mouse testis SOD-1 mRNAs reveals that the 0.93-kb SOD-1 mRNA is primarily non-polysomal, while the 0.80- and 0.73-kb SOD-1 mRNAs are mostly polysome associated. A faster migrating form of the 0.93-kb SOD-1 mRNA is present on polysomes as a result of partial deadenylation. In a cell-free translation system, the 0.73-kb SOD-1 mRNA translates about 2-fold more efficiently than the 0.93-kb SOD-1 mRNA. These data demonstrate that male germ cells transcribe two size classes of SOD-1 mRNAs with different translation potential by utilizing two different promoters, post-meiotic SOD-1 mRNAs undergo adenylation changes, and one of the post-meiotic SOD-1 mRNAs is transcribed during mid-spermiogenesis and translated days later in a partially deadenylated form.
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PMID:In male mouse germ cells, copper-zinc superoxide dismutase utilizes alternative promoters that produce multiple transcripts with different translation potential. 781 80

Recently, tRNALys-3 was cross-linked via its anticodon loop to human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) between residues 230 and 357 (Mishima, Y., and Steitz, J. A. (1995) EMBO J. 14, 2679-2687). Scanning the surface of this region identified three basic amino acids Lys249, Arg307, and Lys311 flanking a small crevice on the p66 thumb subdomain outside the primer-template binding cleft. To assess an interaction of this region with the tRNA anticodon loop, these p66 residues were altered to Glu or Gln. p66 subunits containing K249Q, K311Q, K311E, and a dual R307E/K311E mutation formed a stable dimer with wild type p51. All mutants showed reduced affinity for tRNALys-3 and supported significantly less (-)-strand DNA synthesis from this primer than the parental heterodimer. In contrast, these variants efficiently synthesized HIV-1 (-)-strand strong-stop DNA from oligonucleotide primers and had minimal effect on RNase H activity, retaining endonucleolytic and directed cleavage of an RNA/DNA hybrid. Structural features of binary RT.tRNALys-3 complexes were examined by in situ footprinting, via susceptibility to 1, 10-phenanthroline-copper-mediated cleavage. Unlike wild type RT, mutants p66(K311Q)/p51 and p66(K311E)/p51 failed to protect the tRNA anticodon domain from chemical cleavage, indicating a significant structural alteration in the binary RT.tRNA complex. These results suggest a crevice in the p66 thumb subdomain of HIV-1 RT supports an interaction with the tRNALys-3 anticodon loop critical for efficient (-)-strand DNA synthesis.
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PMID:Mutating a region of HIV-1 reverse transcriptase implicated in tRNA(Lys-3) binding and the consequences for (-)-strand DNA synthesis. 960 66

The data on RNA-RNA interactions between the components of the E. coli translation machinery obtained by X-ray crystallography and chemical methods are compared. The approaches to the study of RNA secondary and tertiary structure are assessed. The following conclusions are made: comparative sequence analysis and compensatory mutations approach both give reliable data on the RNA secondary structure. The chemical modification technique provides good results. Local cleavage of internucleotide bonds by hydroxyl radicals is reliable in the frame of its 40 A resolution, in contrast to the application of copper-phenanthroline complex as a cleavage reagent, which is unreliable. Direct UV irradiation and nitrogen mustard treatment are the best methods of crosslink generation. In vitro transcription is the only good method for the incorporation of nucleotide analogs in RNA. RNase H hydrolysis and/or nucleotide-specific RNases fingerprints must be applied for the crosslink site determination in parallel with reverse transcription.
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PMID:[Study of ribosome structure using the biochemical methods: judgment day]. 1152 44

Metal ions are integral part of some viral proteins and play an important role in their survival and pathogenesis. Zinc, magnesium and copper are the commonest metal ion that binds with viral proteins. Metal ions participate in maturation of genomic RNA, activation and catalytic mechanisms, reverse transcription, initial integration process and protection of newly synthesized DNA, inhibition of proton translocation (M2 protein), minus- and plus-strand transfer, enhance nucleic acid annealing, activation of transcription, integration of viral DNA into specific sites and act as a chaperone of nucleic acid. Metal ions are also required for nucleocapsid protein-transactivation response (TAR)-RNA interactions. In certain situations more than one metal ion is required e.g. RNA cleavage by RNase H. This review underscores the importance of metal ions in the survival and pathogenesis of a large group of viruses and studies on structural basis for metal binding should prove useful in the early design and development of viral inhibitors.
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PMID:Interaction of viral proteins with metal ions: role in maintaining the structure and functions of viruses. 1568 Nov 39