engleski

Colour-based screening for detection of genes affecting palindrome stability in vivo

A palindrome in DNA is a symmetrical sequence consisting of two identical (or near-identical) repeats placed in the inverted orientation one next to the other (or only a few base pairs apart). In such sequence, besides the usual interstrand base pairing, intrastrand base pairing is also possible leading to a formation of secondary structures (hairpins in singlestranded DNA or cruciforms – cross-shaped formations – in doublestranded DNA). Palindromes often play key roles in cis-acting regions of the genome (promoters, origins of replication, etc.). However, the ability of longer palindromes to form stable secondary structures which can hamper vital processes such as transcription and replication of DNA makes them potentially very harmful. Moreover, there is strong evidence that a protein exists which recognizes and cuts cruciform structures, i.e. introduces a double strand break in the DNA. Therefore, cruciforms are a potential source of genome instability which can have devastating consequences. In humans several syndromes accompanied by severe physical malformations and mental retardation are caused by palindrome- related genome instability. A powerful and versatile eukaryotic model organism – yeast Saccharomyces cerevisiae – is a useful tool in palindrome research. We used yeast to systematically investigate the influence of palindrome length and the length of the region between the two repeats on their potential to cause genome instability. Additionally, we constructed yeast strains in which the colour of the colonies (ranging from intensely red to light pink) depends on the stability of an introduced palindrome. Using random mutagenesis and picking colonies with changed colour we selected mutants in which genes involved in palindrome stability were affected. Subsequent analysis and complementation experiments should reveal novel proteins involved in palindrome stability, including the yet unknown cruciform-cutting protein.

palindromes; Saccharomyces cerevisiae; genome stabiliry

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