Sir2p suppresses recombination of replication forks stalled at the replication fork barrier of ribosomal DNA in Saccharomyces cerevisiae.
In the ribosomal DNA (rDNA) of Saccharomyces cerevisiae replication forks progressing against transcription stall at a polar replication fork barrier (RFB) located close to and downstream of the 35S transcription unit. Forks blocked at this barrier are potentially recombinogenic. Plasmids bearing the RFB sequence in its active orientation integrated into the chromosomal rDNA in sir2 mutant cells but not in wild-type cells, indicating that the histone deacetylase silencing protein Sir2 (Sir2p), which also modulates the aging process in yeast, suppresses the recombination competence of forks blocked at the rDNA RFB. Orientation of the RFB sequence in its inactive course or its abolition by FOB1 deletion avoided plasmid integration in sir2 mutant cells, indicating that stalling of the forks in the plasmid context was required for recombination to take place. Altogether these results strongly suggest that one of the functions of Sir2p is to modulate access of the recombination machinery to the forks stalled at the rDNA RFB.
Benguría
Alberto
A
Departamento de Biología Celular y del Desarrollo, Centro de Investigaciones Biológicas (CSIC), Velázquez 144, 28006 Madrid, Spain.
Hernández
Pablo
P
Krimer
Dora B
DB
Schvartzman
Jorge B
JB
D015825:Chromosomes, Fungal; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D006655:Histone Deacetylases / Q000502:physiology*; D010957:Plasmids; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000502:physiology*; D056565:Sirtuin 2; D037761:Sirtuins / Q000502:physiology*
D004271:DNA, Fungal; D004275:DNA, Ribosomal; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases