title: Long inverted repeats are an at-risk motif for recombination in mammalian cells.
abstract: Certain DNA sequence motifs and structures can promote genomic instability. We have explored instability induced in mouse cells by long inverted repeats (LIRs). A cassette was constructed containing a herpes simplex virus thymidine kinase (tk) gene into which was inserted an LIR composed of two inverted copies of a 1.1-kb yeast URA3 gene sequence separated by a 200-bp spacer sequence. The tk gene was introduced into the genome of mouse Ltk(-) fibroblasts either by itself or in conjunction with a closely linked tk gene that was disrupted by an 8-bp XhoI linker insertion; rates of intrachromosomal homologous recombination between the markers were determined. Recombination between the two tk alleles was stimulated 5-fold by the LIR, as compared to a long direct repeat (LDR) insert, resulting in nearly 10(-5) events per cell per generation. Of the tk(+) segregants recovered from LIR-containing cell lines, 14% arose from gene conversions that eliminated the LIR, as compared to 3% of the tk(+) segregants from LDR cell lines, corresponding to a >20-fold increase in deletions at the LIR hotspot. Thus, an LIR, which is a common motif in mammalian genomes, is at risk for the stimulation of homologous recombination and possibly other genetic rearrangements.
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA. awaldman@sc.edu
authors.forename: A S
authors.initials: AS
authors.lastname: Waldman
authors.forename: H
authors.initials: H
authors.lastname: Tran
authors.forename: E C
authors.initials: EC
authors.lastname: Goldsmith
authors.forename: M A
authors.initials: MA
authors.lastname: Resnick
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D051379:Mice; D011995:Recombination, Genetic / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D017931:DNA Primers