X-rays induce interallelic homologous recombination at the human thymidine kinase gene

Journal Article · Mon Jun 01 04:00:00 EDT 1992 · Molecular and Cellular Biology; (United States)

DOI:https://doi.org/10.1128/MCB.12.6.2730· OSTI ID:7199194

Benjamin, M B; Little, J B ^[1]

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1. Harvard Medical School, Boston, MA (United States)

The authors have developed a human lymphoblast cell line for the study of interchromosomal homologous recombination at the endogenous thymidine kinase (tk) gene on chromosome 17. This cell line (designated 6:86) carries unique heterozygous frameshift mutations in exons 4 and 7 of its endogenous tk alleles and can revert to TK+ by frame-restoring mutations, gene conversion, or reciprocal recombination. Line 6:86 reverts spontaneously to TK+ at a frequency of 10[sup [minus]7] to 10[sup [minus]8], and exposures to X-irradiation or the frameshift mutagen ICR-191 induce increased reversion frequencies in a dose-dependent manner. Another cell line (designated 4:2) carries a homozygous exon 7 frameshift and is not expected to revert through mechanisms other than frame-restoring mutation. Line 4:2 reverts to TK+ at a lower spontaneous frequency than does 6:86 but can be induced with similar kinetics by ICR-191. In contrast to line 6:86, however, X rays did not induce detectable reversion of line 4:2. We have characterized a number of 6:86-derived revertants by means of restriction fragment length polymorphism analysis at tk and linked loci, single-strand conformation polymorphisms, and direct transcript sequencing. For X rays, most revertants retain both original mutations in the genomic DNA, and a subset of these frameshift-retaining revertants produce frameshift-free message, indicating that reversion is the result of reciprocal recombination within the tk gene. Frame-restoring point mutations, restoration of original sequences, and phenocopy reversion by acquisition of aminopterin resistance were also found among X-ray-induced revertants, whereas the ICR-191-induced revertants examined show only loss of the exon 7 frameshift.

• OSTI ID: 7199194
• Journal Information: Molecular and Cellular Biology; (United States), Journal Name: Molecular and Cellular Biology; (United States) Vol. 12:6; ISSN 0270-7306; ISSN MCEBD4
• Country of Publication: United States
• Language: English

Related Subjects

550400 -- Genetics
560120* -- Radiation Effects on Biochemicals
Cells
& Tissue Culture
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
ELECTROMAGNETIC RADIATION
GENE RECOMBINATION
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
IONIZING RADIATIONS
RADIATION EFFECTS
RADIATIONS
X RADIATION