A HOMOLOG OF THE BACTERIAL HEAT-SHOCK GENE DNAJ THAT ALTERS PROTEIN SORTING IN YEAST

HEAT-shock proteins have been implicated in assembly of protein complexes 1, correct protein folding 2 and uptake of proteins into organelles 3,4. In Escherichia coli, the heat-shock protein DnaJ and the Hsp70 homologue, DnaK, act together to disassemble a protein complex involved in bacteriophage-lambda replication 5. We report the identification of SCJ1, a gene in the yeast Saccharomyces cerevisiae that encodes a homologue of the bacterial DnaJ protein. SCJ1 was identified by a genetic screen in which increased expression of candidate genes results in missorting of a nuclear-targeted test protein. The predicted amino-acid sequence of SCJ1 is 37% identical to the entire E. coli DnaJ protein. Hybridization experiments indicate that there is a family of yeast genes related to SCJ1. These findings suggest that the Hsp70 DnaK-DnaJ interaction is general to eukaryotes.