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Mol. Cell. Biol., 07 1997, 3614-3628, Vol 17, No. 7
D Yang and AS Waldman
Mouse Ltk- cell lines that contained a herpes simplex virus type 1 (HSV- 1)
thymidine kinase (tk) gene with a 16-bp insertion mutation linked to either
a defective HSV-2 tk gene or a hybrid tk sequence comprised of HSV-1 and
HSV-2 tk sequences were constructed. HSV-1 and HSV-2 tk genes have 81%
nucleotide identity and hence are homeologous. Correction of the insertion
mutant HSV-1 tk gene via recombination with the hybrid tk sequence required
an exchange between homeologous tk sequences, although recombination could
initiate within a region of significant sequence identity. Seven cell lines
containing linked HSV-1 and HSV-1- HSV-2 hybrid tk sequences gave rise to
tk+ segregants at an average rate of 10(-8) events per cell division. DNA
sequencing revealed that each recombinant from these lines displayed an
apparent gene conversion which involved an accurate transfer of an
uninterrupted block of information between homeologous tk sequences.
Conversion tract lengths ranged from 35 to >330 bp. In contrast, cell
lines containing linked HSV-1 and HSV-2 tk sequences with no significant
stretches of sequence identity had an overall rate of homeologous
recombination of <10(-9). One such cell line produced homeologous
recombinants at a rate of 10(- 8). Strikingly, all homeologous recombinants
from this latter cell line were due to crossovers between the HSV-1 and
HSV-2 tk genes. Our results, which provide the first detailed analysis of
homeologous recombination within a mammalian genome, suggest that
rearrangements in mammalian genomes are regulated by the degree of sequence
divergence located at the site of recombination initiation.
Copyright © 1997, American Society for Microbiology
Fine-resolution analysis of products of intrachromosomal homeologous recombination in mammalian cells
Department of Biological Sciences, University of South Carolina, Columbia 29208, USA.
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