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Biomedical subjects

Y N Xia

Publications and source records attributed to Y N Xia.

8 recordsLinked to original sources
PubMed1991

Molecular cloning and characterization of the gene encoding the adenine methyltransferase M.CviRI from Chlorella virus XZ-6E.

The gene encoding the DNA methyltransferase M.CviRI from Chlorella virus XZ-6E was cloned and expressed in Escherichia coli. M.CviRI methylates adenine in TGCA sequences. DNA containing the M.CviRI gene was sequenced and a single open reading frame of 1137 bp was identified which could code for a polypeptide of 379 amino acids with a predicted molecular weight of 42,814. Comparison of the M.CviRI predicted amino acid sequence with another Chlorella virus and 14 bacterial adenine methyltransferases revealed extensive similarity to the other Chlorella virus enzyme.

Amino Acid Sequence↗
PubMed1988

A site-specific single strand endonuclease activity induced by NYs-1 virus infection of a Chlorella-like green alga.

A site-specific endonuclease was isolated from a eukaryotic Chlorella-like green alga infected with the dsDNA-containing virus NYs-1. The enzyme recognizes the sequence 5'-CC-3' and cleaves 5' to the first C. It cleaves 5'-CmC-3' sequences but not 5'-mCC-3' sequences. The enzyme creates breaks in dsDNA whenever two 5'-CC-3' sequences on opposite strands are close enough for the two strands to separate; when the 5'-CC-3' sequences on opposite strands are further apart only a portion of the strands separate. Consequently, NYs-1 endonuclease does not produce a completely stable DNA digestion pattern. The enzyme probably does not cleave ssDNA and definitely does not cleave ssRNA or dsRNA.

Chlorella↗
PubMed1987

IL-3A virus infection of a Chlorella-like green alga induces a DNA restriction endonuclease with novel sequence specificity.

A type II restriction endonuclease, named CviJI, was isolated from a eukaryotic Chlorella-like green alga infected with the dsDNA containing virus IL-3A. CviJI is the first restriction endonuclease to recognize the sequence PuGCPy; CviJI cleaves DNA between the G and C. Methylation of the cytosine in PuGCPy sequences prevents cleavage by CviJI. CviJI cleaved DNA into smaller but defined fragments in the presence of ATP. This "star" activity was stimulated by dithiothreitol and/or S-adenosylmethionine but did not occur under conditions which favor "star" activity of other restriction endonucleases.

Adenosine Triphosphate↗
PubMed1986

Restriction endonuclease activity induced by PBCV-1 virus infection of a Chlorella-like green alga.

An enzyme was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1 which exhibits type II restriction endonuclease activity. The enzyme recognized the sequence GATC and cleaved DNA 5' to the G. Methylation of deoxyadenosine in the GATC sequence inhibited enzyme activity. In vitro the enzyme cleaved host Chlorella nuclear DNA but not viral DNA because host DNA contains GATC and PBCV-1 DNA contains GmATC sequences. PBCV-1 DNA is probably methylated in vivo by the PBCV-1-induced methyltransferase described elsewhere (Y. Xia and J. L. Van Etten, Mol. Cell. Biol. 6:1440-1445). Restriction endonuclease activity was first detected 30 to 60 min after viral infection; the appearance of enzyme activity required de novo protein synthesis, and the enzyme is probably virus encoded. Appearance of enzyme activity coincided with the onset of host DNA degradation after PBCV-1 infection. We propose that the PBCV-1-induced restriction endonuclease participates in host DNA degradation and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.

Base Sequence↗
PubMed1986

DNA methyltransferase induced by PBCV-1 virus infection of a Chlorella-like green alga.

A DNA methyltransferase was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1. The enzyme recognized the sequence GATC and methylated deoxyadenosine solely in GATC sequences. Host DNA, which contains GATC sequences, but not PBCV-1 DNA, which contains GmATC sequences, was a good substrate for the enzyme in vitro. The DNA methyltransferase activity was first detected about 1 h after viral infection; PBCV-1 DNA synthesis and host DNA degradation also began at about this time. The appearance of the DNA methyltransferase activity required de novo protein synthesis, and the enzyme was probably virus encoded. Methylation of DNAs with the PBCV-1-induced methyltransferase conferred resistance of the DNAs to a PBCV-1-induced restriction endonuclease enzyme described previously (Y. Xia, D. E. Burbank, L. Uher, D. Rabussay, and J. L. Van Etten, Mol. Cell. Biol. 6:1430-1439). We propose that the PBCV-1-induced methyltransferase protects viral DNA from the PBCV-1-induced restriction endonuclease and is part of a virus-induced restriction and modification system in PBCV-1-infected Chlorella cells.

Cell Transformation, Viral↗