Degradation Signal Masking by Heterodimerization of MATa2 and MATa1 Blocks Their Mutual Destruction by the Ubiquitin-Proteasome Pathway
Proteolysis by the ubiquitin-proteasome pathway is often regulated, but the mechanisms underlying such regulation remain ill-defined. In Saccharomyces cere-visiae, cell type is controlled by the MAT transcription factors. The a2repressor is a known ubiquitinpathway substrate in a haploid cells. We show that a1 is rapidly degraded in a haploids. In a/a diploids, a2 and a1 are stabilized by heterodimerization. Association depends on N-terminal coiled-coil interactions between a1 and a2. Residues in a2 important for these interactions overlap a critical determinant of an a2 degradation signal, which we delimit by extensive mutagenesis. Our data provide a detailed description of a natural ubiquitin-dependent degradation signal and point to a molecular mechanism for regulated turnover in which proteolytic signals are differentially masked in alternative multiprotein complexes.
Rob Swanson. "Degradation Signal Masking by Heterodimerization of MATa2 and MATa1 Blocks Their Mutual Destruction by the Ubiquitin-Proteasome Pathway" Cell 94 (1998): 217-227. Available at: http://works.bepress.com/rob_swanson/1