DEGRADATION OF THE YEAST MAT-ALPHA-2 TRANSCRIPTIONAL REGULATOR IS MEDIATED BY THE PROTEASOME

Rapid degradation of specific regulatory proteins plays a role in a wi de range of cellular phenomena, including cell cycle progression and t he regulation of cell growth and differentiation. A major mechanism of selective protein turnover in vivo involves a large multi-subunit pro tease known as the proteasome or multi-catalytic proteinase. At the sa me time, the degradation of many cellular proteins requires their cova lent ligation to the polypeptide ubiquitin. Here we show that the yeas t S. cerevisiae MAT alpha 2 repressor, which is known to be ubiquitiny lated in vivo, requires the proteasome for its rapid intracellular pro teolysis.