The functional characterization of a specific gene, or its protein product,
often relies on assessing the consequences of its elimination, usually acc
omplished by gene knockout, ribozyme, antisense, or RNA-mediated interferen
ce (RNAi) technologies. The selective degradation of cellular proteins is m
ediated primarily by the ubiquitin-proteasome pathway. Manipulation of the
ubiquitin-dependent proteolytic machinery to eliminate specific gene produc
ts at the protein level has been previously attempted with some success in
vitro; however, the in vivo efficacy of this approach has not yet been achi
eved. Here we report successful engineering of the substrate receptor of a
major ubiquitin-proteolytic machinery to direct the degradation of otherwis
e stable cellular proteins both in yeast and in mammalian cells.