Single-nucleotide mutation rate increases close to insertions/deletions in eukaryotes
Dacheng Tian, Qiang Wang, Pengfei Zhang, Hitoshi Araki, Sihai Yang, Martin Kreitman, Thomas Nagylaki, Richard Hudson, Joy Bergelson & Jian-Qun Chen
State Key Laboratory of Pharmaceutical Biotechnology, Department of Biology, Nanjing University, Nanjing 210093, China
Abstract:Mutation hotspots are commonly observed in genomic sequences
and certain human disease loci, but general mechanisms for
their formation remain elusive. Here we investigate the distribution
of single-nucleotide changes around insertions/deletions
(indels) in six independent genome comparisons, including primates,
rodents, fruitfly, rice and yeast. In each of these genomic
comparisons, nucleotide divergence (D) is substantially elevated
surrounding indels and decreases monotonically to nearbackground
levels over several hundred bases. D is significantly
correlated with both size and abundance of nearby indels. In
comparisons of closely related species, derived nucleotide substitutions
surrounding indels occur in significantly greater numbers
in the lineage containing the indel than in the one containing
the ancestral (non-indel) allele; the same holds within species for
single-nucleotide mutations surrounding polymorphic indels. We
propose that heterozygosity for an indel is mutagenic to surrounding
sequences, and use yeast genome-wide polymorphism data to
estimate the increase in mutation rate. The consistency of these
patterns within and between species suggests that indel-associated
substitution is a general mutational mechanism.