DNA sequence mutation is the process that fuels
species evolution, but mutations in genes are often harmful. As a form of
defence, organisms have evolved repair mechanisms to correct the DNA sequence
following mutation. One of these mechanisms is termed DNA mismatch repair
(MMR). It corrects mutations that arise during the replication of the genome
during cell division.
A new study, published in Genome Research, has shown for the first time that MMR is targeted to particular regions of the genome, and preferentially repairs genes rather than other, non-genic regions. This finding significantly enhances our understanding of how organisms use MMR to reduce spontaneous mutation rates.
The research was carried out in the Department of Plant Sciences, together with colleagues from Zhejiang University (China) and Lahore University of Management Studies (Pakistan).
The study has important implications for human health, and is particularly useful for understanding the changes that occur in cells during the development of the tumours that underlie cancers.
MMR-deficiency predisposes cells to become tumorous, presumably because MMR-deficient cells lack the gene protection that reduces the risk of mutation in the genes that normally suppress tumour formation. The team have no plans to expand on these implications, but would welcome interest from anyone keen to follow up the study from a medical science perspective.
‘Whilst genes are essential for the biology of organisms, the functions, if any, of the non-genic regions of the genome are less clear’, said Professor Harberd. ‘It is therefore understandable that natural selection may have favoured the relative targeting of MMR to genes rather than non-genic regions. The challenge now is to understand how that targeting works.’