Differential processing of leading- and lagging-strand ends at Saccharomyces cerevisiae telomeres revealed by the absence of Rad27p nuclease.
Saccharomyces cerevisiae strains lacking the Rad27p nuclease, a homolog of the mammalian FEN-1 protein, display an accumulation of extensive single-stranded G-tails at telomeres. Furthermore, the lengths of telomeric repeats become very heterogeneous. These phenotypes could be the result of aberrant Okazaki fragment processing of the C-rich strand, elongation of the G-rich strand by telomerase, or an abnormally high activity of the nucleolytic activities required to process leading-strand ends. To distinguish among these possibilities, we analyzed strains carrying a deletion of the RAD27 gene and also lacking genes required for in vivo telomerase activity. The results show that double-mutant strains died more rapidly than strains lacking only telomerase components. Furthermore, in such strains there is a significant reduction in the signals for G-tails as compared to those detected in rad27delta cells. The results from studies of the replication intermediates of a linear plasmid in rad27delta cells are consistent with the idea that only one end of the plasmid acquires extensive G-tails, presumably the end made by lagging-strand synthesis. These data further support the notion that chromosome ends have differential requirements for end processing, depending on whether the ends were replicated by leading- or lagging-strand synthesis.
Parenteau
Julie
J
Département de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbooke, Sherbooke, Quebec J1H 5N4, Canada.
Wellinger
Raymund J
RJ
D001482:Base Composition; D001483:Base Sequence; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D045585:Flap Endonucleases; D017353:Gene Deletion; D005800:Genes, Fungal; D008954:Models, Biological; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D019098:Telomerase / Q000235:genetics / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*
D004271:DNA, Fungal; D004277:DNA, Single-Stranded; D029701:Saccharomyces cerevisiae Proteins; D019098:Telomerase; D004706:Endodeoxyribonucleases; D045585:Flap Endonucleases; C468323:RAD27 protein, S cerevisiae