title: Differential effects of base-pair mismatch on intrachromosomal versus extrachromosomal recombination in mouse cells.
abstract: To initially determine the effect that base-pair mismatch has on homologous recombination in mammalian cells, we have studied genetic recombination between thymidine kinase (tk) gene sequences from herpes simplex virus 1 and 2. These tk genes are approximately 81% homologous at the nucleotide level. We observed that, in mouse LTK- cells, intrachromosomal recombination between type 1 and type 2 tk sequences is reduced by a factor of at least 1000 relative to the rate of intrachromosomal recombination between homologous type 1 tk sequences. In sharp contrast, the rate of intermolecular or intramolecular extrachromosomal recombination between the heterologous tk sequences introduced by calcium phosphate or microinjection was reduced only by a factor of 3 to 15 compared with extrachromosomal homologous tk crosses. Our results suggest differences between the mechanisms of extrachromosomal and intrachromosomal recombination in mammalian cells.
mesh_terms: D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes / Q000378:metabolism; D015245:Deoxyribonuclease BamHI; D015247:Deoxyribonuclease HindIII; D015252:Deoxyribonucleases, Type II Site-Specific; D051379:Mice; D009693:Nucleic Acid Hybridization; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D013937:Thymidine Kinase; D004262:DNA Restriction Enzymes; D015245:Deoxyribonuclease BamHI; D015247:Deoxyribonuclease HindIII; C032824:ATCGAT-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific