SIR1/YKR101W Summary Help

Standard Name SIR1 1
Systematic Name YKR101W
Feature Type ORF, Verified
Description Protein involved in silencing at mating-type loci HML and HMR; recruitment to silent chromatin requires interactions with Orc1p and with Sir4p, through a common Sir1p domain; binds to centromeric chromatin (2, 3, 4 and see Summary Paragraph)
Name Description Silent Information Regulator 1
Chromosomal Location
ChrXI:640540 to 642504 | ORF Map | GBrowse
Genetic position: 84 cM
Gene Ontology Annotations All SIR1 GO evidence and references
  View Computational GO annotations for SIR1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 4 genes
Classical genetics
reduction of function
Large-scale survey
133 total interaction(s) for 70 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 8
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 7
  • Co-crystal Structure: 2
  • Co-fractionation: 1
  • Co-localization: 5
  • PCA: 1
  • Reconstituted Complex: 3
  • Two-hybrid: 14

Genetic Interactions
  • Dosage Rescue: 16
  • Negative Genetic: 20
  • Phenotypic Enhancement: 27
  • Phenotypic Suppression: 4
  • Positive Genetic: 1
  • Synthetic Growth Defect: 12
  • Synthetic Lethality: 2
  • Synthetic Rescue: 9

Expression Summary
Length (a.a.) 654
Molecular Weight (Da) 76,933
Isoelectric Point (pI) 9.41
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXI:640540 to 642504 | ORF Map | GBrowse
Genetic position: 84 cM
Last Update Coordinates: 2011-02-03 | Sequence: 2009-02-20
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..1965 640540..642504 2011-02-03 2009-02-20
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000001809

SIR1 is one of four Silent Information Regulator genes in yeast. It encodes a nuclear protein that helps silence transcription of the cryptic mating type loci HML and HMR (1, 2, 5). Unlike repressors that act by binding to promoters, the Sir proteins help repress transcription by creating a silent chromatin stucture in a gene- and promoter-independent manner (6, 7). The Sir proteins do not bind DNA directly, but rather seem to act via histones and other DNA binding proteins (6, 8, 9). The exact means by which the Sir proteins create a silenced domain is unknown.

Silencing at HML and HMR depends on the presence of a regulatory chromosomal domain that contains binding sites for such multifunctional nuclear proteins as the Origin Recognition Complex (ORC), Abf1p, and Rap1p, which are in turn thought to be recognized by silencing-specific proteins such as Sir1p, Sir2p, Sir3p, and Sir4p (10, 11, 5). The congregation of all these factors leads to the assembly of a chromatin silencing complex, and a domain of silenced chromatin (7). Sir1p seems to be involved in the establishment rather than the maintenance of a silenced state at HML and HMR (12, 13, 14). Sir1p likely recognizes a silencer element in the DNA through its interactions with ORC, because a small region of Sir1p found to be necessary for recognizing the HMR silencer was the same region of Sir1p required for interacting with Orc1p (11). Also, a Gal4-Sir1p fusion tethered at HMR bypassed the requirement for both the silencer element and ORC in silencing that locus, but still required passage through S phase and the presence of the other Sir proteins for silencing (5, 14, 15). Sir1p is the only Sir protein that appears not to be involved in telomeric silencing (13)

Last updated: 1999-09-01 Contact SGD

References cited on this page View Complete Literature Guide for SIR1
1) Rine J, et al.  (1979) A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci. Genetics 93(4):877-901
2) Rine J and Herskowitz I  (1987) Four genes responsible for a position effect on expression from HML and HMR in Saccharomyces cerevisiae. Genetics 116(1):9-22
3) Sharp JA, et al.  (2003) The budding yeast silencing protein Sir1 is a functional component of centromeric chromatin. Genes Dev 17(19):2356-61
4) Bose ME, et al.  (2004) The origin recognition complex and Sir4 protein recruit Sir1p to yeast silent chromatin through independent interactions requiring a common Sir1p domain. Mol Cell Biol 24(2):774-86
5) Triolo T and Sternglanz R  (1996) Role of interactions between the origin recognition complex and SIR1 in transcriptional silencing. Nature 381(6579):251-3
6) Laurenson P and Rine J  (1992) Silencers, silencing, and heritable transcriptional states. Microbiol Rev 56(4):543-60
7) Loo S and Rine J  (1994) Silencers and domains of generalized repression. Science 264(5166):1768-71
8) Shore D  (1994) RAP1: a protean regulator in yeast. Trends Genet 10(11):408-12
9) Loo S and Rine J  (1995) Silencing and heritable domains of gene expression. Annu Rev Cell Dev Biol 11:519-48
10) Kimmerly W, et al.  (1988) Roles of two DNA-binding factors in replication, segregation and transcriptional repression mediated by a yeast silencer. EMBO J 7(7):2241-53
11) Gardner KA, et al.  (1999) A region of the Sir1 protein dedicated to recognition of a silencer and required for interaction with the Orc1 protein in saccharomyces cerevisiae. Genetics 151(1):31-44
12) Pillus L and Rine J  (1989) Epigenetic inheritance of transcriptional states in S. cerevisiae. Cell 59(4):637-47
13) Aparicio OM, et al.  (1991) Modifiers of position effect are shared between telomeric and silent mating-type loci in S. cerevisiae. Cell 66(6):1279-87
14) Fox CA, et al.  (1997) The origin recognition complex, SIR1, and the S phase requirement for silencing. Science 276(5318):1547-51
15) Chien CT, et al.  (1993) Targeting of SIR1 protein establishes transcriptional silencing at HM loci and telomeres in yeast. Cell 75(3):531-41