Recombinogenicity of palidndromic sequences in selected mutants of yeast Saccharomyces cerevisiae

Palindromski sljedovi nukleotida izvor su genetičke nestabilnosti u svim organizmima jer u molekuli DNA formiraju sekundarne strukture (kruciforme i ukosnice) koje se in vivo prevode u dvolančani lom. Međutim, još nije identificiran kvaščev protein koji cijepa kruciforme u genomu kvasca Saccharomyces cerevisiae. U ovom radu korišten je eksperimentalni sustav u kojem se promjena rekombinogenosti palindroma očituje lako uočljivom promjenom boje kolonije, a istražen je utjecaj nekoliko rezolvaza i strukturno-specifičnih endonukleaza koje bi mogle cijepati kruciform. Ustanovljeno je da nedostatak rezolvaze Mus81 ili Yen1 kao i strukturno-specifične endonukleaze Pso2 koja cijepa ukosnice ne utječe na stabilnost 150 pb dugačkog palindroma u genomu kvasca. Ovaj rezultat mogao bi biti posljedica redundantne uloge ovih proteina te je moguće da se njihov utjecaj na stabilnost palindroma može primijetiti tek u višestrukom mutantu.Palindromic sequences are the source of genetic instability in all living organisms. They form secondary structures in DNA (cruciforms and hairpins) which are processed into a double-strand break in vivo. However, the yeast protein that cleaves cruciforms in Saccharomyces cerevisiae genome has not yet been identified. In this research, several resolvases and structure specific endonucleases that could cleave cruciform were tested using the yeast experimental system in which the change of palindrome recombinogenicity is easily observed via colony color change. The absence of Mus81 or Yen1 resolvase, as well as the absence of a structure specific endonuclease Pso2, does not affect the stability of a 150 bp palindrome in the yeast genome. This finding could be a consequence of the overlapping roles of Mus81 and Yen1 proteins indicating that the effect on a palindrome stability could be observed in a double or a triple mutant