Identification of a specific protein factor defective in group A xeroderma pigmentosum cells.
A protein factor which corrects the defect in xeroderma pigmentosum cells belonging to complementation group A (XP-A cells) was detected in a cell extract prepared from calf thymus. The activity of this factor was measured as the amount of unscheduled DNA synthesis (UDS) reappearing in UV-irradiated XP-A cells after microinjection of the extract. The native molecular mass of this factor was estimated to be 80 kDa by gel-filtration and 25 kDa by glycerol gradient centrifugation. The activity was, however, recovered at a position corresponding to 43 kDa after renaturation on an SDS-PAGE gel. The isoelectric point was determined to be approximately 7.5 by measuring the activity after renaturation on an IEF gel. These values were obtained with a partially purified sample. A spot corresponding to these values was detected on two-dimensional gel electrophoresis with a highly purified sample recovered from an SDS-PAGE gel. The purified protein stimulated UDS specifically in the XP-A cells and endowed the cells with a normal level of UV-resistance. The XP-A cells injected with the factor also showed a normal level of UDS after treatment with either 4HAQO or psoralen plus UV-A. This factor (XP-A complementing factor; XP-ACF) may be involved in the repair of DNA damage induced by various agents.
Sugano
T
T
Institute for Medical Genetics, Kumamoto University Medical School.
Uchida
T
T
Yamaizumi
M
M
D000818:Animals; D002417:Cattle; D002460:Cell Line; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D004591:Electrophoresis, Polyacrylamide Gel; D011564:Furocoumarins / Q000494:pharmacology; D005816:Genetic Complementation Test; D006801:Humans; D008970:Molecular Weight; D011489:Protein Denaturation; D011506:Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D013950:Thymus Gland / Q000737:chemistry*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
D011564:Furocoumarins; D011506:Proteins