The human heat-shock protein family. Expression of a novel heat-inducible HSP70 (HSP70B′) and isolation of its cDNA and genomic DNA

Abstract

The human heat-shock protein multigene family comprises several highly conserved proteins with structural and functional properties in common, but which vary in the extent of their inducibility in response to metabolic stress. We have isolated and characterized a novel human HSP70 cDNA, HSP70B' cDNA, and its corresponding gene sequence. HSP70B' cDNA hybrid-selected an mRNA encoding a more basic 70 kDa heat-shock protein that both the major stress-inducible HSP70 and constitutively expressed HSC70 heat-shock proteins, which in common with other heat-shock 70 kDa proteins bound ATP. The complete HSP70B' gene was sequenced and, like the major inducible HSP70 gene, is devoid of introns. The HSP70B' gene has 77% sequence similarity to the HSP70 gene and 70% similarity to HSC70 cDNA, with greatest sequence divergence towards the 3'-terminus. The HSP70B' gene represents a functional gene, as indicated by Northern-blot analysis with specific oligonucleotides, hybrid-selected translation with a specific 3' cDNA sequence and S1 nuclease protection experiments. In contrast with HSP70 mRNA, which is present at low concentrations in HeLa cells and readily induced by heat or CdCl2 treatment in both fibroblasts and HeLa cells, HSP70B' mRNA was induced only at higher temperature and showed no basal expression. The differences in patterns of induction may be due to the special features of the promoter region of the HSP70B' gene.

Cell number‐dependent regulation of Hsp70B′ expression: Evidence of an extracellular regulator

“…Mutational analysis of these two elements in particular have shown them to be required for basal expression of human Hsp70 genes (Greene et al, 1987). Site-directed mutagenesis experiments show that point mutations in the TATA box resulting in a higher consensus can give rise to activation at much lower temperatures (Leung et al, 1990). Another basal factor, GAGA is also involved in enhancing promoter accessibility in unstressed conditions.…”

“…Here, we report an analysis of Hsp70B 0 regulation. Unlike Hsp72, Hsp70B 0 is strictly inducible, having little or no basal detectable level in most cells (Leung et al, 1990;Parsian et al, 2000), whereas Hsp72 is relatively abundant even in unstressed cells. In fact, Hsp70B 0 induction has been used as a highly sensitive biomarker of cellular stress (Leung et al, 1990;Wada et al, 2005;Wang et al, 2005).…”

“…Unlike Hsp72, Hsp70B 0 is strictly inducible, having little or no basal detectable level in most cells (Leung et al, 1990;Parsian et al, 2000), whereas Hsp72 is relatively abundant even in unstressed cells. In fact, Hsp70B 0 induction has been used as a highly sensitive biomarker of cellular stress (Leung et al, 1990;Wada et al, 2005;Wang et al, 2005). Hsp70B 0 is also interesting from an evolutionary point of view, as the Hsp70B 0 gene HSPA6 appears to have arisen after the divergence of rodents and humans (Parsian et al, 2000).…”

Endothelial nitric oxide synthase induces heat shock protein HSPA6 (HSP70B′) in human arterial smooth muscle cells

“…HSPA6 is a unique human specific gene with no introns, with little known about its function [28]. HSPA6 is a strictly inducible member of the HSP 70 family with little or no basal M A N U S C R I P T…”

Members of the heat-shock protein 70 family promote cancer cell growth by distinct mechanisms

“…Hsp70 is expressed only at low or undetectable levels in most unstressed normal cells and tissues, but its expression is rapidly induced by a variety of physical and chemical stresses, and therefore it is often called the major stress-inducible Hsp70. Finally, Hsp70-6 (Hsp70BЈ) represents a poorly studied intronless member of the family that shows almost no basal expression and is induced only by extreme stresses (Leung et al 1990).…”