HMRA1/YCR097W Summary Help

Standard Name HMRA1
Systematic Name YCR097W
Alias YCR097WB
Feature Type ORF, Verified|silenced_gene
Description Silenced copy of a1 at HMR; homeobox corepressor that interacts with Alpha2p to repress haploid-specific gene transcription in diploid cells (1, 2, 3, 4, 5, 6 and see Summary Paragraph)
Name Description Hidden Mat Right A
Chromosomal Location
ChrIII:293835 to 294321 | ORF Map | GBrowse
Gene Ontology Annotations All HMRA1 GO evidence and references
  View Computational GO annotations for HMRA1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 3 genes
Classical genetics
18 total interaction(s) for 8 unique genes/features.
Physical Interactions
  • Affinity Capture-RNA: 3
  • Co-crystal Structure: 4
  • Reconstituted Complex: 8

Genetic Interactions
  • Dosage Rescue: 3

Expression Summary
Length (a.a.) 126
Molecular Weight (Da) 14,803
Isoelectric Point (pI) 10.46
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrIII:293835 to 294321 | ORF Map | GBrowse
This feature is contained within: HMR
Last Update Coordinates: 2011-02-03 | Sequence: 1997-01-28
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..105 293835..293939 2011-02-03 1997-01-28
Intron 106..159 293940..293993 2011-02-03 1997-01-28
CDS 160..405 293994..294239 2011-02-03 1997-01-28
Intron 406..457 294240..294291 2011-02-03 1997-01-28
CDS 458..487 294292..294321 2011-02-03 1997-01-28
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 SGDIDS000000694

a1 is one of two genes encoded by the a mating type cassette in S. cerevisiae (5). The mating type of S. cerevisiae is determined by the genetic composition of the MAT locus (7, 5, 6). Haploids of the a mating type express the genes a1 and a2 from the MAT locus while haploids of the alpha mating type express alpha1 and alpha2 from MAT (7, 5, 6). Some of the cells within a given colony are capable of switching mating type by changing the genetic composition of the MAT locus (8); more information on mating type switching can be found in the summary paragraph for MAT and references cited therein. Diploid cells are normally heterozygous (a/alpha) at the MAT locus (7, 5, 6).

a1 encodes a homeodomain protein involved in transcriptional regulation of mating-type-specific genes (1, 3, 5, 6). The a1 protein is produced in haploid MATa cells, but does not play any known role in a-specific gene expression, and is rapidly degraded (5, 9). In a/alpha diploid cells, a1p interacts with another homeodomain protein, alpha2p, to bind DNA as a heterodimer to repress transcription of haploid-specific genes (1, 5, 3, 6, 4, 2, 10). The interaction between a1p and alpha2p stabilizes both proteins, and alters their DNA binding specificities (1, 4, 9, 11).

Note: The maps and sequences within SGD reflect the fact that a MATalpha strain was used in the systematic sequencing project. Accordingly, there are two copies of the alpha1 and alpha2 genes; one pair (MATalpha1/YCR040W and MATalpha2/YCR039C) corresponds to the MAT locus, and the other (HMLalpha1/YCL066W and HMLalpha2/YCL067C) to the HML locus. There are ORFs assigned to the copies of a1 and a2 found at HMR (HMRa1/YCR097W) and (HMRa2/YCR096C); locus entries are included for MATa1 and MATa2 but they do not have ORFs associated with them. There are GenBank sequences available from all of the locus pages describing a1, a2, alpha1, and alpha2; the Genbank accession for the MATa cassette is V01313.

Last updated: 2000-08-15 Contact SGD

References cited on this page View Complete Literature Guide for HMRA1
1) Goutte C and Johnson AD  (1988) a1 protein alters the DNA binding specificity of alpha 2 repressor. Cell 52(6):875-82
2) Goutte C and Johnson AD  (1994) Recognition of a DNA operator by a dimer composed of two different homeodomain proteins. EMBO J 13(6):1434-42
3) Dranginis AM  (1990) Binding of yeast a1 and alpha 2 as a heterodimer to the operator DNA of a haploid-specific gene. Nature 347(6294):682-5
4) Goutte C and Johnson AD  (1993) Yeast a1 and alpha 2 homeodomain proteins form a DNA-binding activity with properties distinct from those of either protein. J Mol Biol 233(3):359-71
5) Herskowitz I  (1989) A regulatory hierarchy for cell specialization in yeast. Nature 342(6251):749-57
6) Herskowitz I, et al.  (1992) "Mating-type determination and mating-type interconversion in Saccharomyces cerevisiae." Pp. 583-656 in The Molecular and Cellular Biology of the Yeast Saccharomyces: Gene Expression, edited by Jones EW, Pringle JR and Broach JR. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press
7) Herskowitz I  (1983) Cellular differentiation, cell lineages, and transposable genetic cassettes in yeast. Curr Top Dev Biol 18:1-14
8) Haber JE  (1998) Mating-type gene switching in Saccharomyces cerevisiae. Annu Rev Genet 32:561-99
9) Johnson PR, et al.  (1998) Degradation signal masking by heterodimerization of MATalpha2 and MATa1 blocks their mutual destruction by the ubiquitin-proteasome pathway. Cell 94(2):217-27
10) Li T, et al.  (1998) Crystal structure of the MATa1/MATalpha2 homeodomain heterodimer in complex with DNA containing an A-tract. Nucleic Acids Res 26(24):5707-18
11) Stark MR, et al.  (1999) A trans-acting peptide activates the yeast a1 repressor by raising its DNA-binding affinity. EMBO J 18(6):1621-9