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| Xeroderma pigmentosum variant heterozygotes show reduced levels of recovery of replicative DNA synthesis in the presence of caffeine after ultraviolet irradiation |
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| Author(s): Itoh T, Linn S, Kamide R, Tokushige H, Katori N, Hosaka Y, Yamaizumi M |
| Source: JOURNAL OF INVESTIGATIVE DERMATOLOGY Volume: 115 Issue: 6 Pages: 981-985 Published: DEC 2000 |
| Times Cited: 9 References: 19 |
| Abstract: Patients with xeroderma pigmentosum variant show clinical photosensitivity, skin neoplasias induced by ultraviolet light, and defective postreplication repair, but normal nucleotide excision repair. We recently reported an alternative, simple method for the diagnosis of xeroderma pigmentosum variant that measures by autoradiography three cellular markers for DNA repair after ultraviolet irradiation: unscheduled DNA synthesis, recovery of RNA synthesis, and recovery of replicative DNA synthesis. Among hereditary photosensitive disorders, including other xeroderma pigmentosum groups, Cockayne syndrome, and a newly established ultraviolet-sensitive syndrome, only xeroderma pigmentosum variant cells exhibited normal unscheduled DNA synthesis, normal recovery of RNA synthesis, but reduced recovery of replicative DNA synthesis (51 +/- 6% the rate relative to normal controls). This reduction of recovery of replicative DNA synthesis was enhanced in the presence of a nontoxic level of caffeine to 36 +/- 5%. In this study we assess the cellular markers in two independent families that included two photosensitive patients that were identified as xeroderma pigmentosum variant. Cells from heterozygotic parents showed normal levels of unscheduled DNA synthesis, recovery of RNA synthesis, and recovery of replicative DNA synthesis, but reduced rates of recovery of replicative DNA synthesis in the presence of 1 mM caffeine (53 +/- 8% relative to the normal control). Furthermore, with a colony-forming assay, the cells showed normal survival by ultraviolet without caffeine, but slightly reduced survival by ultraviolet with 1 mM caffeine present. In one family, we confirmed inheritance of two heterozygous mis-sense mutations. One mutation is an A -->G transition at nucleotide 1840 that generates a K535E mis-sense mutation. Another mutation is an A -->C transversion at nucleotide 2003 that generates a K589 mis-sense mutation. Each of these mutations were absent in 52 unrelated Japanese individuals. These results suggest that xeroderma pigmentosum variant heterozygotes can be identified by their sensitivity to ultraviolet irradiation in the presence of nontoxic levels of caffeine. |
| Document Type: Article |
| Language: English |
| Reprint Address: Itoh, T (reprint author), Univ Calif Berkeley, Dept Mol & Cell Biol, Div Biochem & Cell Biol, 229 Stanley Hall, Berkeley, CA 94720 USA |
Addresses:
1. Univ Calif Berkeley, Dept Mol & Cell Biol, Div Biochem & Cell Biol, Berkeley, CA 94720 USA
2. Kumamoto Univ, Inst Mol Embryol & Genet, Dept Cell Genet, Kumamoto, Japan
3. Jikei Univ, Sch Med, Dept Dermatol, Tokyo, Japan
4. Showa Univ, Sch Med, Dept Plast & Reconstruct Surg, Tokyo, Japan |
| Publisher: BLACKWELL SCIENCE INC, 350 MAIN ST, MALDEN, MA 02148 USA |
| Subject Category: Dermatology |
| IDS Number: 390FT |
| ISSN: 0022-202X |
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