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EFFECTS OF ULTRAVIOLET LIGHT ON THYMIDINE INCORPORATION AND DNA CHAIN ELONGATION IN PHOTOREACTIVABLE INSECT CELLS
Author(s) -
Styer Susan C.,
Meechan Paul J.,
Griffiths T. Daniel
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb05564.x
Subject(s) - pyrimidine dimer , thymidine , photolyase , dna synthesis , dna damage , dna , dna repair , biology , elongation , chemistry , microbiology and biotechnology , biochemistry , materials science , ultimate tensile strength , metallurgy
–An insect cell line, IAL‐PID2, was exposed to UV and analyzed for its ability to incorporate [ 3 H]‐thymidine and to elongate replicon‐sized DNA fragments. After exposure to 5 or 10 J/m 2 UV, the cells exhibited a rapid and prolonged depression in the rate of thymidine incorporation. Photoreactivation reduced this depression but did not entirely reverse it. For exposures of 5 J/m 2 or above, full recovery did not occur until 18 h after exposure. The blockage of fork progression after UV exposure was fluence‐dependent, with replication segments after exposure to 20 J/m 2 being shorter than those observed after exposure to 10 J/m 2 . Immediately after exposure to either 10 or 20 J/m 2 , photoreactivation reversed blockage of fork progression, indicating that the (5–6) cyclobutyl pyrimidine dimer is responsible for blockage. This also indicates that blockage of fork progression may not be the only factor responsible for the prolonged depression seen in thymidine incorporation. Three hours after exposure to either 10 or 20 J/m 2 , replication segments were still significantly shorter than control segments. Photoreactivation completely reversed blockage after exposure to 10 J/m 2 , but did not completely reverse blockage after exposure to 20 J/m 2 , indicating that at such fluences, other lesions may play a role in UV‐induced blockage of fork progression.