Identification of an essential gene, l(3)73Ai, with a dominant temperature-sensitive lethal allele, encoding a Drosophila proteasome subunit.

Proteasomes are multicatalytic proteinase complexes that function as a major nonlysosomal proteolytic system in all eukaryotes. These particles are made up of 13-15 nonidentical subunits, and they exhibit multiple endopeptidase activities that promote the intracellular turnover of abnormal polypeptides and short-lived regulatory proteins. Although the biochemical characterization of proteasomes has been quite extensive, and although a number of the genes encoding proteasome subunits have been cloned from various organisms, there is still much to be learned about their function in vivo and what role(s) they might play during development. Here, we report the identification of the l(3)73Ai1 allele of Drosophila melanogaster as a dominant temperature-sensitive lethal mutation in a gene encoding a component of the proteasome, thus opening the way for future genetic and developmental studies on this important proteolytic system in a higher eukaryote.