Characterization and sequence of a mouse hsp70 gene and its expression in mouse cell lines

A heat-inducible member of the mouse hsp70 gene family has been isolated and characterized. The gene, hsp70.1, has a primary transcript of 2.8 kb before and 3.1-3.5 kb after polyadenylation. It includes a 645-nucleotide (nt) 3′-nontranslated terminus and a 225-nt 5t́ leader. The leader sequence is unusual in that it contains a 33-nt triple tandem repeat element proximal to the ATG codon. As expected, a single open reading frame encodes a 642-amino acid (aa) 70-kDa protein with 95% aa homology and 91% nt homology to a human hsp70 gene. While there is no homology through the 5′- and 3′-nontranslated regions, the human and mouse hsp70 gene promoters can be aligned to give 65% homology. Of three mouse cell lines studied, two expressed the 3.1- to 3.5-kb mRNA during heat shock. One line also expressed an additional, smaller, 2.6-kb hsp70 mRNA transcribed from a separate gene(s). Mouse erythroleukemia cells were unresponsive to heat shock, with neither hsp70 RNA being induced by heat shock. These results suggest that cell lineage has a major influence on the cellular response to heat shock and that the response is not universal in all cell types.