engleski

Recombinogenic potential of palindromic sequences is determined by their size and position in the yeast genome

Genomes of many organisms, from bacteria to humans, are known to contain significant proportion of palindromic sequences. These sequences are frequently found in different regulatory, cis-acting regions of the genome, but are also known to provoke different types of potentially deleterious genetic alterations, such as deletions or translocations. This property of longer palindromes is likely an outcome of their ability to form secondary structures which can be targets for cleavage by structure specific endonucleases, leading to double strand breaks, which could in turn lead to harmful genome rearrangements. Since recombinogenicity of palindromes is clearly size related, we decided to sistematically investigate how the step by step increase in the size of a palindrome will affect its genetic stability. We demonstrate that palindromic sequences become recombinogenic only after they attain a critical size of approximately 70 bp, and that palindrome stimulated recombination is completely dependent on the SAE2 gene. Recombinogenicity of palindromic sequences is attributed to their capacity to form secondary structures and our results suggest that, when palindromes are shorter than 70 bp, such structures either do not form in vivo, or are very unstable and short lived. Additionaly, suppression of palindrome recombinogenicity may be crucial for the maintenance of genetic stability in genomes containing significant number of palindromes even longer than 100 bp, like human genome.

Palindromic sequences; Genetic stability; Yeast; Saccharomyces cerevisiae; SAE2; Recombination

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