title: Suppression of intrachromosomal gene conversion in mammalian cells by small degrees of sequence divergence.
abstract: Pairs of closely linked defective herpes simplex virus (HSV) thymidine kinase (tk) gene sequences exhibiting various nucleotide heterologies were introduced into the genome of mouse Ltk- cells. Recombination events were recovered by selecting for the correction of a 16-bp insertion mutation in one of the tk sequences. We had previously shown that when two tk sequences shared a region of 232 bp of homology, interruption of the homology by two single nucleotide heterologies placed 19 bp apart reduced recombination nearly 20-fold. We now report that either one of the nucleotide heterologies alone reduces recombination only about 2.5-fold, indicating that the original pair of single nucleotide heterologies acted synergistically to inhibit recombination. We tested a variety of pairs of single nucleotide heterologies and determined that they reduced recombination from 7- to 175-fold. Substrates potentially leading to G-G or C-C mispairs in presumptive heteroduplex DNA (hDNA) intermediates displayed a particularly low rate of recombination. Additional experiments suggested that increased sequence divergence causes a shortening of gene conversion tracts. Collectively, our results suggest that suppression of recombination between diverged sequences is mediated via processing of a mispaired hDNA intermediate.
authors: Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA.
authors: T
authors: T
authors: Lukacsovich
authors: A S
authors: AS
authors: Waldman
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D005785:Gene Conversion; D005814:Genes, Viral; D007739:L Cells; D051379:Mice; D016254:Mutagenesis, Insertional; D009692:Nucleic Acid Heteroduplexes / Q000235:genetics; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics
chemical_list: D017931:DNA Primers; D009692:Nucleic Acid Heteroduplexes; D004247:DNA; D013937:Thymidine Kinase