Question

Recall the use of combinatorial control in regulation of the S. cerevisiae mating type specific gene expression. Describe how Mcm1 serves to repress and activate transcription of target genes in haploid MAT α cells?

Answer 1

Mcm1 in 'S. cerevisiae' acts as both a transcriptional activator and repressor in MAT α cells, depending on its interaction with other proteins, facilitating complex gene regulation.

Step-by-step explanation:

In the budding yeast Saccharomyces cerevisiae, Mcm1 plays a central role in the regulation of mating type specific gene expression in haploid MAT α cells. The Mcm1 protein serves both as a transcriptional activator and a repressor depending on its interactions with other regulatory proteins. To activate transcription, Mcm1 binds to enhancer elements in the promoters of target genes. However, when Mcm1 interacts with alpha-specific repressors like α2, it represses transcription by preventing the binding of the transcription activation complex to gene promoters. Therefore, the role of Mcm1 in gene regulation showcases the complexity of combinatorial control, where the combination of different transcription factors and co-regulators determine the patterns and levels of gene expression.