The carboxy-terminal tail of the homeo domain protein α2 is required for function with a second homeo domain protein

Abstract

The homeo domain protein α2 from Saccharomyces cerevisiae has two roles in the a/α cell: With MCM1, α2 tarns off transcription of a-specific genes; with a1 (a second homeo domain protein), α2 represses transcription of haploid-specific genes. From the carboxy-terminal side of the α2 homeo domain extends an unstructured 22-amino-acid residue tail. In this paper we show that the carboxy-terminal tail of α2 is required for formation of a stable a1/α2-operator complex and is thus required for a1/α2-mediated repression of transcription. In contrast, the tail is dispensable for α2/MCM1-mediated repression. These results indicate that a short, unstructured tail mediates the interaction between two homeo domain proteins.