Excision repair of pyrimidine dimers from simian virus 40 minichromosomes in vitro

Journal Article · Sat Aug 25 04:00:00 EDT 1984 · J. Biol. Chem.; (United States)

OSTI ID:5269475

Evans, D H; Linn, S

The ability of DNA repair enzymes to carry out excision repair of pyrimidine dimers in SV40 minichromosomes irradiated with UV light was examined. Half of the dimers were substrate for the DNA glycosylase activity of phage T4 UV endonuclease immediately after irradiation, but this limit decreased to 27% after 2 h at 0/sup 0/C. The apyrimidinic (AP) endonuclease activity of the enzyme did not incise all of the AP sites created by glycosylase, although all AP sites were substrate for HeLa AP endonuclease II. After incision by the T4 enzyme, excision was mediated by HeLa DNase V (acting with an exonuclease present in the chromatin preparation). Under physiological salt conditions, excision did not proceed beyond the damaged nucleotides in DNA or chromatin. With chromatin, 70% of the accessible dimers were removed, but at a rate slower than for DNA. Finally, HeLa DNA polymerase ..beta.. was able to fill the short gaps created after dimer excision, and these patches were sealed by T4 DNA ligase. Overall, roughly 30% of the sites incised by the endonuclease were ultimately sealed by the ligase. The resistance of some sites was due to interference with the ligase by the chromatin structure, as only 30-40% of the nicks created in chromatin by pancreatic DNase could be sealed by T4 or HeLa DNA ligases. The overall excision repair process did not disrupt the chromatin structure, since the repair label was recovered in Form I DNA present in 75 S condensed minichromosomes. Although other factors might affect the rate, it appears that the enzymes utilized could carry out excision repair of chromatin to a limit near that observed in mammalian cells in vivo.

• Research Organization: Univ. of California, Berkeley
• OSTI ID: 5269475
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 259:16; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

560111* -- Radiation Effects on Biochemicals-- In Vitro-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHROMOSOMES
DNA-ASE
ELECTROMAGNETIC RADIATION
ENZYME ACTIVITY
ENZYMES
ESTERASES
GLYCOSYL HYDROLASES
HYDROLASES
IN VITRO
LABELLED COMPOUNDS
MICROORGANISMS
PARASITES
PHOSPHODIESTERASES
PYRIMIDINE DIMERS
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
SIMIAN VIRUS
TRITIUM COMPOUNDS
ULTRAVIOLET RADIATION
VIRUSES