title: Specific action of T4 endonuclease V on damaged DNA in xeroderma pigmentosum cells in vivo.
abstract: The specific action of T4 endonuclease V on damaged DNA in xeroderma pigmentosum cells was examined using an in vivo assay system with hemagglutinating virus of Japan (Sendai virus) inactivated by UV light. A clear dose response was observed between the level of UV-induce unscheduled DNA synthesis of xeroderma pigmentosum cells and the amount of T4 endonuclease V activity added. The T4 enzyme was unstable in human cells, and its half-life was 3 hr. Fractions derived from an extract of Escherichia coli infected with T4V1, a mutant defective in the endonuclease V gene, showed no ability to restore the UV-induced unscheduled DNA synthesis of xeroderma pigmentosum cells. However, fractions derived from an extract of T4D-infected E. coli with endonuclease V activity were effective. The T4 enzyme was effective in xeroderma pigmentosum cells on DNA damaged by UV light but not in cells damaged by 4-nitroquinoline 1-oxide. The results of these experiments show that the T4 enzyme has a specific action on human cell DNA in vivo. Treatment with the T4 enzyme increased the survival of group A xeroderma pigmentosum cells after UV irradiation.
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000494:pharmacology; D002460:Cell Line; D003090:Coliphages / Q000201:enzymology*; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism*; D004260:DNA Repair; D004720:Endonucleases / Q000378:metabolism*; D005796:Genes; D006801:Humans; D010222:Parainfluenza Virus 1, Human / Q000528:radiation effects; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D015112:4-Nitroquinoline-1-oxide; D004247:DNA; D004720:Endonucleases