Molecular evolution of the HSP70 multigene family.

Eukaryotic genomes encode multiple 70-kDa heat-shock proteins (HSP70s). The Saccharomyces cerevisiae HSP70 family is comprised of eight members. Here we present the nucleotide sequence of the SSA3 and SSB2 genes, completing the nucleotide sequence data for the yeast HSP70 family.

Structure and regulation of the SSA4 HSP70 gene of Saccharomyces cerevisiae.

SSA4 is the only one of five heat-inducible HSP70 genes in Saccharomyces cerevisiae whose expression is restricted to conditions of stress. Comparison of the nucleotide sequences of the SSA4 gene with other HSP70 genes indicates that it diverged from its most closely related yeast homologues hundreds of millions of years ago. However, a high degree of identity has been maintained between Ssa4p and other yeast 70-kDa heat-shock proteins at the amino acid level suggesting, in light of its distinct pattern of regulation, that it performs an important function.

A review of the role of 70 kDa heat shock proteins in protein translocation across membranes.

The compartmentalization of essential hsp70 proteins indicates that hsp70s carry out crucial functions in several compartments of the cell. The use of conditional mutants has allowed study of the cellular processes that require hsp70 function. For efficient translocation of proteins across membranes hsp70s are required in the cytoplasm, as well as in the matrix of mitochondria and in the lumen of the endoplasmic reticulum.

Regulation of a yeast HSP70 gene by a cAMP responsive transcriptional control element.

HSP70 genes exhibit complex regulation in response to stress and a variety of cellular and developmental events. The SSA3 HSP70 gene of Saccharomyces cerevisiae is activated at the transcriptional level under conditions of nutrient limitation. Analysis of deletions revealed that cis-acting DNA sequences present immediately upstream and downstream of the previously identified heat shock elements (UASHS) mediate this regulation.