Bacteriophage T4 encodes an RNase H which removes RNA primers made by the T4 DNA replication system in vitro.
RNase H activity increases markedly after bacteriophage T4 infection of Escherichia coli MIC2003, an RNase H-deficient host. We have extensively purified the RNase H from these T4-infected cells and have shown that the RNase H activity copurifies with a 5' to 3' DNA exonuclease activity. The N-terminal sequence of a 35-kDa protein copurifying with the RNase H activity matches the terminus of the predicted product of an open reading frame (designated ORF A or 33.2) upstream of T4 gene 33, identified previously by Hahn and co-workers (Hahn, S., Kruse, U., and Rüger, W. (1986) Nucleic Acids Res. 14, 9311-9327). Plasmids containing ORF A under the control of the T7 promoter express RNase H and 5' to 3' DNA exonuclease activities as well as a protein that comigrates on sodium dodecyl sulfate-polyacrylamide gels with the 35-kDa protein present in the RNase H purified from T4-infected cells. T4 RNase H removes the pentamer RNA primers from DNA chains initiated by the T4 primase-helicase (gene products 61 and 41). Addition of T4 RNase H and T4 DNA ligase leads to extensive joining of discontinuous lagging strand fragments in the T4 DNA replication system in vitro.
Section on Nucleic Acid Biochemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
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Hollingsworth
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D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D019915:DNA Primase; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis*; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000378:metabolism; D005814:Genes, Viral; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009841:Oligonucleotides / Q000378:metabolism; D012313:RNA / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000378:metabolism; D016914:Ribonuclease H; D013379:Substrate Specificity; D013604:T-Phages / Q000201:enzymology* / Q000235:genetics; D015678:Viral Structural Proteins / Q000235:genetics*; D014779:Virus Replication
D004279:DNA, Viral; D009841:Oligonucleotides; C034477:RNA primers; D015678:Viral Structural Proteins; D012313:RNA; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D004722:Endoribonucleases; D005090:Exodeoxyribonucleases; D016914:Ribonuclease H