SUMMARY PARAGRAPH for HMLALPHA2
alpha2 is one of two genes encoded by the alpha mating type cassette in S. cerevisiae. The mating type of S. cerevisiae is determined by the genetic composition of the MAT locus (10, 8, 9). 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 (10, 8, 9). Some of the cells within a given colony are capable of switching mating type by changing the genetic composition of the MAT locus (11); 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 (10, 8, 9).
alpha2 encodes a homeodomain protein involved in transcriptional regulation of mating type-specific genes (8, 9). In MATalpha haploid cells, alpha2p associates with the transcription factor Mcm1p to repress transcription of a-specific genes (8, 9). alpha2p binds DNA as a homodimer; Mcm1p determines the DNA-binding affinity and specificity of the complex (3, 2, 7, 12, 5, 8, 9). Transcriptional repression of a-specific genes also involves the repressors Ssn6p and Tup1p, which interact with alpha2p (13, 14, 15). alpha2p and Mcm1p also play a role in donor preference in mating type switching (16, 17, 11).
In a/alpha diploid cells, alpha2p interacts with another homeodomain protein, a1p, to bind DNA as a heterodimer to repress transcription of haploid-specific genes (1, 8, 18, 9, 6, 4, 19). The interaction between a1p and alpha2p stabilizes both proteins, and alters their DNA binding specificities (1, 6, 20, 21). Transcriptional repression of a-specific genes by alpha2p and Mcm1p also occurs in dipoloid cells(9).
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 <3482>HMR (HMRa1/YCR097W) and (<000000692>HMRa2/YCR096C); locus entries are included for MAT, 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 V01313.000000692>3482>
Last updated: 2004-11-05