The regulation of DNA repair during serum stimulation of quiescent cells was examined in normal human cells, in fibroblasts from three xeroderma pigmentosum complementation groups (A, C, and D), in xeroderma pigmentosum variant cells, and in ataxia telangiectasia cells. The regulation of nucleotide excision repair was examined by exposing cells to ultraviolet irradiation at discrete intervals a...

The cell line HepG2 is derived from a well differentiated human hepatoblastoma, which retains many of the morphological characteristics of liver parenchymal cells. These cells at passages greater than 95 were found to metabolically activate carcinogens to genotoxic metabolites. The addition of 6.8 microM 1-methyl-3-nitro-1-nitrosoguanidine, 5.3 microM 4-nitroquinoline-N-oxide, and 4-20.3 microM...

Induction of unscheduled DNA synthesis (UDS) by 8-methoxypsoralen (8-MOP) plus ultraviolet A (UV-A) (PUVA) was investigated in the epidermis of female hairless mice by means of an in vivo--in vitro assay using a liquid scintillation counting method. Groups of three to five 8-week-old female hairless mice had 8-MOP applied once onto two areas of the back after stripping of the stratum corneum wi...

Heretofore, unscheduled DMA synthesis (UDS) induced by DMA-damaging chemicals has been measured in nonreplicating human fibroblasts by autoradiographic meth ods that are not readily applicable to organotypic epithe lial cell cultures. In order to evaluate the range of chemi cal sensitivity and DNA repair response of human skin epithelial cells, we have developed a novel semiquantitative in vitr...

Nucleotide excision repair (NER) removes the major UV-photolesions from cellular DNA. In humans, compromised NER activity is the cause of several photosensitive diseases, one of which is the skin-cancer predisposition disorder, xeroderma pigmentosum (XP). Two assays commonly used in measurement of NER activity are 'unscheduled DNA synthesis (UDS)', and 'recovery of RNA synthesis (RRS)', the lat...

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 nu...

Interactions of novobiocin (NB) and nalidixic acid (NA) with thiols were investigated in vitro in thymic (T-) and splenic (S-) cells of the rat, by determining nucleic acid synthesis as well as nucleoid sedimentation and viscosity of alkaline cell lysates. In T-cells NB, at concentrations of 0.35-1.4 mM, increased unscheduled DNA synthesis (UDS) and RNA synthesis (RNS), whereas S-cells underwen...

A crucial regulation for maintaining genome integrity in eukaryotes is to limit DNA replication in S phase to only one round. Several models have been proposed; one of which, the licensing model, predicted that formation of the nuclear membrane restricts access to chromatin to a positive replication factor. Cdt1, a factor binding to origins and recruiting the MCM2-7 helicase, has been identifie...