Separation-of-function mutants of yeast Ku80 reveal a Yku80p-Sir4p interaction involved in telomeric silencing.
The Saccharomyces cerevisiae Ku heterodimer comprising Yku70p and Yku80p is involved in telomere maintenance and DNA repair by the pathway of non-homologous end joining. It is also a key regulator of transcriptional silencing of genes placed in close proximity to telomeres. Here, we describe the identification of separation-of-function mutants of Yku80p that exhibit defects in silencing but not DNA repair and show that these mutations map to an evolutionarily conserved domain within Yku80p. Furthermore, we reveal that Yku80p interacts with the silent information regulator protein Sir4p and that this interaction is mediated by the N-terminal 200 amino acid residues of Sir4p. Notably, this interaction also requires the region of Yku80p that contains the sites of the silencing defective mutations. Finally, we show that these mutations impair the Yku80p-Sir4p interaction and recruitment of Sir3p to telomeric regions in vivo. Taken together with other data, these findings indicate that the Yku80p-Sir4p interaction plays a vital role in the assembly of telomeric heterochromatin.
Roy
Rajat
R
Wellcome Trust/Cancer Research UK Institute of Cancer and Developmental Biology, and Deparment of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK.
Meier
Bettina
B
McAinsh
Andrew D
AD
Feldmann
Heidi M
HM
Jackson
Stephen P
SP
D000595:Amino Acid Sequence; D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics*; D001483:Base Sequence; D004265:DNA Helicases; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D020868:Gene Silencing; D005838:Genotype; D006801:Humans; D000072200:Ku Autoantigen; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000235:genetics*
D034961:Antigens, Nuclear; D017931:DNA Primers; D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen