Slx5 promotes transcriptional silencing and is required for robust growth in the absence of Sir2.
The broadly conserved Sir2 NAD(+)-dependent deacetylase is required for chromatin silencing. Here we report the discovery of physical and functional links between Sir2 and Slx5 (Hex3), a RING domain protein and subunit of the Slx5/8 complex, [corrected] which is a ubiquitin E3 ligase that targets sumoylated proteins. Slx5 interacted with Sir2 by two-hybrid and glutathione S-transferase-binding assays and was found to promote silencing of genes at telomeric or ribosomal DNA (rDNA) loci. However, deletion of SLX5 had no detectable effect on the distribution of silent chromatin components and only slightly altered the deacetylation of histone H4 lysine 16 at the telomere. In vivo assays indicated that Sir2-dependent silencing was functionally intact in the absence of Slx5. Although no previous reports suggest that Sir2 contributes to the fitness of yeast populations, we found that Sir2 was required for maximal growth in slx5Delta mutant cells. A similar requirement was observed for mutants of the SUMO isopeptidase Ulp2/Smt4. The contribution of Sir2 to optimal growth was not due to known Sir2 roles in mating-type determination or rDNA maintenance but was connected to a role of sumoylation in transcriptional silencing. These results indicate that Sir2 and Slx5 jointly contribute to transcriptional silencing and robust cellular growth.
Darst
Russell P
RP
Department of Molecular Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0347, USA.
Garcia
Sandra N
SN
Koch
Melissa R
MR
Pillus
Lorraine
L
D004275:DNA, Ribosomal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000939:Epitopes; D016193:G1 Phase; D006655:Histone Deacetylases / Q000172:deficiency* / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000172:deficiency* / Q000235:genetics; D056565:Sirtuin 2; D037761:Sirtuins / Q000172:deficiency* / Q000235:genetics; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D016615:Telomere / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D000939:Epitopes; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases; C515573:Slx5 protein, S cerevisiae