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Palindromes: required but risky (CROSBI ID 493219)

Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija

Svetec, Ivan-Krešimir ; Lisnić, Berislav ; Zgaga, Zoran Palindromes: required but risky // EMBO Lecture Course on New Developments in Genomics for Biomedicine / Dolinar, Marko ; Gubenšek, Franc (ur.). Ljubljana: Institut "Jožef Štefan", Ljubljana, 2003. str. 54-54-x

Podaci o odgovornosti

Svetec, Ivan-Krešimir ; Lisnić, Berislav ; Zgaga, Zoran

engleski

Palindromes: required but risky

Genomes of many organisms, especially higher eukaryotes, are known to contain a significant proportion of repeated sequences. Inverted repeats present a special class of repeated sequences due their ability to form intrastrand base pairs creating secondary structures known as hairpins and cruciforms. Although such motifs are frequently found in cis-acting genetic elements, they can also promote genomic instability in different organisms, from bacteria to humans. For example, in the yeast Saccharomyces cerevisiae it was shown that a palindrome (perfect head-to-head inverted repeat) formed by two 1.0-kb-inverted repeats can stimulate recombination in the adjacent region up to 17, 000-fold. Instability of palindromes is generally connected with their ability to form cruciforms, which either block the progression of DNA replication or are recognized and transformed into double-stranded brakes by a cruciform-cutting endonuclease. In our previous work we investigated the influence of a 102 bp palindrome inserted in the yeast CYC1 region on plasmid integration into the yeast genome. Palindromic sequence had strong influence on the spectrum of recombination events revealed by Southern blot analysis of transformants, but integration was stimulated only if the palindromic insertion was present both in the plasmid and in the chromosomal copy of the CYC1 gene. Here we decided to study the influence of palindromes on intrachromosomal "pop-out" recombination. For this purpose we constructed several isogenic yeast strains containing two directly repeated CYC1 regions separated by intervening sequence bearing the yeast URA3 gene. Palindromes of different sizes were inserted either within the intervening sequence (up to 112 bp) or within one copy of the CYC1 region (up to 110 bp). Each strain was grown to the stationary phase in the minimal supplemented medium without uracil and pop-out recombinants were selected as uracil auxotrophs on the agar plates containing 5-fluoro-orotic acid. The presence of palindromes longer then approximately 50 bp stimulated recombination and with the longest palindromes used (in either location) the rate of pop-out recombination was increased 4-fold. Molecular analysis of pop-out recombinants revealed a striking difference between the strains containing palindromic and non-palindromic (control strain) insertions. In the strain containing the palindrome, only 1 out of 80 uracile auxotrophs retained the insertion in the CYC1 region, while in control strain the insertion was detected in 18 out of 60 recombinants. We also determined the number of perfect palindromes in the Saccharomyces cerevisiae chromosomes and we found that the short palindromes (4 to 8 bp) are underrepresented, while the palindromes longer than 12 bp are over represented. However, in accordance with our results, the largest palindrome found was 44-bp-long and it is placed on the yeast chromosome 4.

palindrome; recombination; yeast

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Podaci o prilogu

54-54-x.

2003.

objavljeno

Podaci o matičnoj publikaciji

EMBO Lecture Course on New Developments in Genomics for Biomedicine

Dolinar, Marko ; Gubenšek, Franc

Ljubljana: Institut "Jožef Štefan", Ljubljana

Podaci o skupu

EMBO Lecture Course on New Developments in Genomics for Biomedicine

predavanje

08.04.2003-13.04.2003

Brdo kod Kranja, Slovenija

Povezanost rada

Biotehnologija