title: Interchromosomal crossover in human cells is associated with long gene conversion tracts.
abstract: Crossovers have rarely been observed in specific association with interchromosomal gene conversion in mammalian cells. In this investigation two isogenic human B-lymphoblastoid cell lines, TI-112 and TSCER2, were used to select for I-SceI-induced gene conversions that restored function at the selectable thymidine kinase locus. Additionally, a haplotype linkage analysis methodology enabled the rigorous detection of all crossover-associated convertants, whether or not they exhibited loss of heterozygosity. This methodology also permitted characterization of conversion tract length and structure. In TI-112, gene conversion tracts were required to be complex in tract structure and at least 7.0 kb in order to be selectable. The results demonstrated that 85% (39/46) of TI-112 convertants extended more than 11.2 kb and 48% also exhibited a crossover, suggesting a mechanistic link between long tracts and crossover. In contrast, continuous tracts as short as 98 bp are selectable in TSCER2, although selectable gene conversion tracts could include a wide range of lengths. Indeed, only 16% (14/95) of TSCER2 convertants were crossover associated, further suggesting a link between long tracts and crossover. Overall, these results demonstrate that gene conversion tracts can be long in human cells and that crossovers are observable when long tracts are recoverable.
authors.affiliation: University of California, Department of Cell Biology and Neuroscience and Environmental Toxicology Graduate Program, 2211 Biological Sciences Building, Riverside, CA 92521, USA.
authors.forename: Efrem A H
authors.initials: EA
authors.lastname: Neuwirth
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Honma
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Grosovsky
mesh_terms: D000483:Alleles; D045744:Cell Line, Tumor; D020090:Chromosome Segregation / Q000235:genetics; D002877:Chromosomes, Human / Q000235:genetics*; D003434:Crossing Over, Genetic / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D005785:Gene Conversion / Q000235:genetics*; D008040:Genetic Linkage; D005819:Genetic Markers; D006801:Humans; D019656:Loss of Heterozygosity / Q000235:genetics; D008957:Models, Genetic; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D005819:Genetic Markers; D029701:Saccharomyces cerevisiae Proteins; C066166:AI4 protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific