title: Molecular nature of ultraviolet B light-induced deletions in the murine epidermis.
abstract: Depletion of the stratospheric ozone layer leads to an increase in ambient UV loads, which are expected to raise skin cancer incidences. Tumor development in the skin could be a multistep process in which various genetic alterations, such as point mutations and deletions, occur successively. Here, we demonstrate that UVB irradiation efficiently induces deletions in the epidermis using a novel transgenic mouse, gpt delta. In this mouse model, deletions in lambda DNA integrated in the chromosome are preferentially selected as Spi(-) (sensitive to P2 interference) phages, which can then be subjected to molecular analysis. The mice were exposed to UVB at single doses of 0.3, 0.5, 1.0, 1.5, and 2.0 kJ/m(2). After 4 weeks, lambda phage was rescued from the genomic DNA of the epidermis by in vitro packaging reactions. The mutant frequencies of Spi(-) with large deletions in the epidermis increased >15-fold at a UVB dose of 0.5 kJ/m(2) over the control. Molecular sizes of most of the large deletions were >1000 bp. More than one-half of the large deletions occurred between short direct-repeat sequences from 1 to 6 bp, and the remainder had flush ends. In the unirradiated mouse, almost all of the Spi(-) mutants were 1-bp frameshifts in runs of identical bases. These results suggest that UVB irradiation induces deletions in the murine epidermis, and most of the deletions are generated through end-joining of double strand breaks in DNA.
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Horiguchi
authors.forename: K I
authors.initials: KI
authors.lastname: Masumura
authors.forename: H
authors.initials: H
authors.lastname: Ikehata
authors.forename: T
authors.initials: T
authors.lastname: Ono
authors.forename: Y
authors.initials: Y
authors.lastname: Kanke
authors.forename: T
authors.initials: T
authors.lastname: Nohmi
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004817:Epidermis / Q000502:physiology / Q000528:radiation effects*; D004926:Escherichia coli / Q000235:genetics / Q000821:virology; D029968:Escherichia coli Proteins; D005260:Female; D016368:Frameshift Mutation; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010430:Pentosyltransferases; D011506:Proteins; D017384:Sequence Deletion; D012878:Skin Neoplasms / Q000209:etiology / Q000235:genetics; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D001426:Bacterial Proteins; D004279:DNA, Viral; D029968:Escherichia coli Proteins; D011506:Proteins; D010430:Pentosyltransferases; C071962:Gpt protein, E coli