Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The initial endonuclease cleavage site in 32 S pre-rRNA (precursor to rRNA) is located within the rate rDNA sequence by S1-nuclease protection mapping of purified nucleolar 28 S rRNA and 12 S pre-rRNA. The heterogeneous 5'- and 3'-termini of these rRNA abut and map within two CTC motifs in tSi2 (internal transcribed spacer 2) located at 50-65 and 4-20 base-pairs upstream from the homogeneous 5'-end of the 28 S rRNA gene. These results show that multiple endonuclease cleavages occur at CUC sites in tSi2 to generate 28 S rRNA and 12 S pre-rRNA with heterogeneous 5'- and 3'-termini, respectively. These molecules have to be processed further to yield mature 28 S and 5.8 S rRNA. Thermal-denaturation studies revealed that the base-pairing association in the 12 S pre-rRNA:28 S rRNA complex is markedly stronger than that in the 5.8 S:28 S rRNA complex. The sequence of about one-quarter (1322 base-pairs) of the 5'-part of the rat 28 S rDNA was determined. A computer search reveals the possibility that the cleavage sites in the CUC motifs are single-stranded, flanked by strongly base-paired GC tracts, involving tSi2 and 28 S rRNA sequences. The subsequent nuclease cleavages, generating the termini of mature rRNA, seem to be directed by secondary-structure interactions between 5.8 S and 28 S rRNA segments in pre-rRNA. An analysis for base-pairing among evolutionarily conserved sequences in 32 S pre-rRNA suggests that the cleavages yielding mature 5.8 S and 28 S rRNA are directed by base-pairing between (i) the 3'-terminus of 5.8 S rRNA and the 5'-terminus of 28 S rRNA and (ii) the 5'-terminus of 5.8 S rRNA and internal sequences in domain I of 28 S rRNA. A general model for primary- and secondary-structure interactions in pre-rRNA processing is proposed, and its implications for ribosome biogenesis in eukaryotes are briefly discussed.
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PMID:Localization and structure of endonuclease cleavage sites involved in the processing of the rat 32S precursor to ribosomal RNA. 633 4

We previously reported on a variant of the herpes simplex type 1 (HSV-1) strain 17 syn+, named 17 hep syn, capable of forming giant polykaryocytes (syncytia) in tissue culture and which induced a striking alteration in the pathogenesis of infection in vivo. Following footpad inoculation of mice, 17 hep syn infection resulted in a marked clinicopathologic acute inflammatory response of the inoculated limb and mice died without antecedant limb paralysis typical of the wild-type 17 syn+ infection. The syncytial and pathogenic phenotypes were mapped to a cloned 670-base pair Kpnl-Pstl (0.345-0.351 map units) DNA fragment encoding the carboxy terminal portion of the glycoprotein B (gB). In this report, we focus on the genetics of the region of the 17 hep syn gB gene that conferred both the syncytial and pathogenic phenotypes to 17 syn+. Five 17 syn+ x 17 hep syn syncytial recombinant viruses, R1-R5, generated in marker transfer experiments with cloned 17 hep syn fragments containing gB sequences, produced 17 hep syn-like disease in mice. Sequence analysis of the Kpnl-Pstl fragment of 17 hep syn revealed a single base pair change when compared to the 17 syn+ sequence, predicting an alanine (GCC codon) to valine (GTC codon) amino acid substitution at residue 825 of the mature gB protein, plus loss of an Ncol restriction endonuclease site. Southern blot analysis of Ncol digests of viral DNAs showed that all of the recombinants except R4 contained the same mutation as 17 hep syn. The syncytial phenotype of R4 was, however, mapped to the same region as 17 hep syn and the other recombinants, and the DNA sequence of the 670-base pair Kpnl-Pstl clone of R4 revealed another single base pair change predicting a leucine (CTC codon) to histadine (CAC codon) amino acid substitution at residue 787 of gB. The mutant gBs did not effect viral growth as all of the recombinant viruses had similar in vitro replication kinetics to wild-type HSV-1. These data provide direct evidence that at least two mutations can exist in the carboxy terminus of gB of HSV-1 that promote syncytial formation in vitro and effect pathogenesis in vivo.
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PMID:Two novel single amino acid syncytial mutations in the carboxy terminus of glycoprotein B of herpes simplex virus type 1 confer a unique pathogenic phenotype. 839 Jul 47

We induced the B-to-A conformational transition by ethanol in a linearized pUC19 DNA. A primer extension method was used in combination with UV light irradiation to follow the transition, based on pausing of DNA synthesis due to the presence of damaged bases in the template. Primer extension data highly correlated with the results of another method monitoring the B-A transition, i.e. inhibition of restriction endonuclease cleavage of UV light-irradiated DNA. Primer extension enabled us to locate damaged nucleotides within the region of interest. Most damaged nucleotides were located in B-form trimers, exclusively containing both pyrimidine bases (TTC, TCT, CTC, and CTT), and in a cytosine tetramer. The amount of damaged bases decreased in the course of B-A transition. Some of the damage even disappeared in the A-form, which mainly concerns the C(4) and C(3) blocks. The cleavage was nearly restored in the A-form within this region (Eco88I). On the contrary the decrease of damage was less significant with thymine dimers, only dropping to 50-60% of the B-form level. Consequently, the cleavage with EcoRI and HindIII remained mostly as before the transition (75% and 60% of uncleaved DNA preserved). We found significant differences in the B- and A-form pattern of UV light-damaged bases within the same region (polylinker) of DNA embedded within long (plasmid) or short (127 bp fragment) DNA molecules. The B-A transition of the fragment was found less cooperative than with linearized plasmid, which was confirmed by both CD spectroscopy and restriction cleavage inhibition.
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PMID:Photochemical probing of the B--a conformational transition in a linearized pUC19 DNA and its polylinker region. 1696

The discovery of small noncoding RNAs (sncRNAs) with regulatory functions is a recent breakthrough in biology. Among sncRNAs, microRNA (miRNA), derived from host or virus, has emerged as elements with high importance in control of viral replication and host responses. However, the expression pattern and functional aspects of other types of sncRNAs, following viral infection, are unexplored. In order to define expression patterns of sncRNAs, as well as to discover novel regulatory sncRNAs in response to viral infection, we applied deep sequencing to cells infected with human respiratory syncytial virus (RSV), the most common cause of bronchiolitis and pneumonia in babies. RSV infection leads to abundant production of transfer RNA (tRNA)-derived RNA Fragments (tRFs) that are ~30 nucleotides (nts) long and correspond to the 5'-half of mature tRNAs. At least one tRF, which is derived from tRNA-Glu-CTC, represses target mRNA in the cytoplasm and promotes RSV replication. This demonstrates that this tRF is not a random by-product of tRNA degradation but a functional molecule. The biogenesis of this tRF is also specific, as it is mediated by the endonuclease angiogenin (ANG), not by other nucleases. In summary, our study presents novel information on the induction of a functional tRF by viral infection.
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PMID:Identification and functional characterization of tRNA-derived RNA fragments (tRFs) in respiratory syncytial virus infection. 2318 36