Effects of microinjected photoreactivating enzyme on thymine dimer removal and DNA repair synthesis in normal human and xeroderma pigmentosum fibroblasts

Journal Article · Thu Mar 15 00:00:00 EST 1990 · Cancer Research; (USA)

OSTI ID:6853782

Roza, L; Vermeulen, W; Bergen Henegouwen, J B; Eker, A P; Jaspers, N G; Lohman, P H; Hoeijmakers, J H ^[1]

---

1. TNO Medical Biological Laboratory, Rijswijk (Netherlands)

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 difference is preferential removal of some type(s) of nondimer lesions, 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.

• OSTI ID: 6853782
• Journal Information: Cancer Research; (USA), Vol. 50:6; ISSN 0008-5472
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
LYASES
RADIOSENSITIVITY EFFECTS
PYRIMIDINE DIMERS
RADIOINDUCTION
XP CELLS
DNA REPAIR
DOSE-RESPONSE RELATIONSHIPS
FIBROBLASTS
FLUORESCENCE
GENETIC RADIATION EFFECTS
MAN
MONOCLONAL ANTIBODIES
ULTRAVIOLET RADIATION
XERODERMA PIGMENTOSUM
ANIMAL CELLS
ANIMALS
ANTIBODIES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CONNECTIVE TISSUE CELLS
DISEASES
ELECTROMAGNETIC RADIATION
ENZYMES
GENETIC EFFECTS
LUMINESCENCE
MAMMALS
PRIMATES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
SKIN DISEASES
SOMATIC CELLS
VERTEBRATES
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture