Print Email Facebook Twitter Effects of microinjected photoreactivity enzyme on thymine dimer removal and DNA repair synthesis in normal human and xeroderma pigmentosum fibroblasts Title Effects of microinjected photoreactivity enzyme on thymine dimer removal and DNA repair synthesis in normal human and xeroderma pigmentosum fibroblasts Author Medisch Biologisch Laboratorium TNO Roza, L. Vermeulen, W. Bergen Henegouwen, J.B.A. Eker, A.P.M. Jaspers, N.G.J. Lohman, P.H.M. Hoeijmakers, J.H.J. Publication year 1990 Abstract UV-induced thymine dimers (10 J/m2 of UV-C) were assayed in normal human and xeroderma pigmentosum (XP) fibroblasts with a monoclonal antibody against these dimers and quantitative fluorescence microscopy. In repair-proficient cells dimer-specific immunofluorescence gradually decreased with time, reaching about 25% of the initial fluorescence after 27 h. Rapid disappearance of dimers was observed in cells which had been microinjected with yeast photoreactivating enzyme prior to UV irradiation. This photoreactivation (PHR) was light dependent and (virtually) complete within 15 min of PHR illumination. In general, PHR of dimers strongly reduces UV-induced unscheduled DNA synthesis (UDS). However, when PHR was applied immediately after UV irradiation, UDS remained unchanged initially; the decrease set in only after 30 min. When PHR was performed 2 h after UV exposure, UDS dropped without delay. An explanation for this differnece is preferential removal of some type(s) of nondimer lesions, e.g., (6-4)photoproducts, which is responsible for the PHR-resistant UDS immediately following UV irradiation. After the rapid removal of these photoproducts, the bulk of UDS is due to dimer repair. From the rapid effect of dimer removal by PHR on UDS it can be deduced that the excision of dimers up to the repair synthesis step takes considerably less than 30 min. Also in XP fibroblasts of various complementation groups the effect of PHR was investigated. The immunochemical dimer assay showed rapid PHR-dependent removal comparable to that in normal cells. However, the decrease of (residual) UDS due to PHR was absent (in XP-D) or much delayed (in XP-A and -E) compared to normal cells. This supports the idea that in these XP cells preferential repair of nondimer lesions does occur, but at a much lower rate. Subject Deoxyribodipyrimidine photolyaseThymineDNALyasePyrimidine dimerCell cultureDNA damageDNA repairHumanHuman cellPriority journalXeroderma pigmentosumDNA replicationFibroblastKineticsMetabolismMicroinjectionRadiation exposureRadiation responseReference valueUltraviolet radiationCells, CulturedDeoxyribodipyrimidine Photo-LyaseDNADose-Response Relationship, RadiationFibroblastsHumanKineticsLyasesMicroinjectionsPyrimidine DimersReference ValuesSupport, Non-U.S. Gov'tUltraviolet RaysXeroderma Pigmentosum To reference this document use: http://resolver.tudelft.nl/uuid:1e6676e8-130f-4600-9faa-85a92eeb48be TNO identifier 231091 ISSN 0008-5472 Source Cancer Research, 50 (50), 1905-1910 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.