title: Defective DNA endonuclease activities in Fanconi's anemia cells, complementation groups A and B.
abstract: Cells from patients with the inherited disorder, Fanconi's anemia (FA), were analyzed for endonucleases which recognize DNA interstrand cross-links and monoadducts produced by psoralen plus UVA irradiation. Two chromatin-associated DNA endonuclease activities, defective in their ability to incise DNA-containing adducts produced by psoralen plus UVA light, have been identified and isolated in nuclei of FA cells. In FA complementation group A (FA-A) cells, one endonuclease activity, pI 4.6, which recognizes psoralen intercalation and interstrand cross-links, has 25% of the activity of the normal human endonuclease, pI 4.6, on 8-methoxypsoralen (8-MOP) plus UVA-damaged DNA. In FA complementation group B (FA-B) cells, a second endonuclease activity, pI 7.6, which recognizes psoralen monoadducts, has 50% and 55% of the activity, respectively, of the corresponding normal endonuclease on 8-MOP or angelicin plus UVA-damaged DNA. Kinetic analysis reveals that both the FA-A endonuclease activity, pI 4.6, and the FA-B endonuclease activity, pI 7.6, have decreased affinity for psoralen plus UVA-damaged DNA. Both the normal and FA endonucleases showed approximately a 2.5-fold increase in activity on psoralen plus UVA-damaged reconstituted nucleosomal DNA compared to damaged non-nucleosomal DNA, indicating that interaction of these FA endonucleases with nucleosomal DNA is not impaired. These deficiencies in two nuclear DNA endonuclease activities from FA-A and FA-B cells correlate with decreased levels of unscheduled DNA synthesis (UDS), in response to 8-MOP or angelicin plus UVA irradiation, in these cells in culture.
authors.affiliation: Department of Laboratory Medicine and Pathology, UMDNJ-New Jersey Medical School, Newark 07103.
authors.forename: M W
authors.initials: MW
authors.lastname: Lambert
authors.forename: G J
authors.initials: GJ
authors.lastname: Tsongalis
authors.forename: W C
authors.initials: WC
authors.lastname: Lambert
authors.forename: B
authors.initials: B
authors.lastname: Hang
authors.forename: D D
authors.initials: DD
authors.lastname: Parrish
mesh_terms: D002460:Cell Line; D004247:DNA / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004260:DNA Repair; D003720:Densitometry; D003851:Deoxyribonucleases / Q000378:metabolism*; D005199:Fanconi Anemia / Q000201:enzymology*; D005363:Ficusin; D011564:Furocoumarins / Q000378:metabolism; D005816:Genetic Complementation Test; D006801:Humans; D007364:Intercalating Agents / Q000378:metabolism; D007700:Kinetics; D008730:Methoxsalen; D014466:Ultraviolet Rays
chemical_list: D011564:Furocoumarins; D007364:Intercalating Agents; D004247:DNA; C011659:angelicin; D003851:Deoxyribonucleases; D005363:Ficusin; D008730:Methoxsalen