Murine 86- and 84-kDa heat shock proteins, cDNA sequences, chromosome assignments, and evolutionary origins

The two forms of the approximately 90-kDa murine heat shock protein, referred to as HSP86 and HSP84, are coded for by separate but related genes. A full-length nucleotide sequence of the cDNA coding for HSP86 from a chemically induced tumor, Meth A, was determined. Sequences from a number of peptides from HSP86 were found to be in complete agreement with the nucleotide sequence. The HSP84 sequence from the same tumor was also completed. HSP86 and HSP84 are acidic polypeptides 733 and 724 amino acids long with calculated molecular weights of 84,796 and 83,290, respectively. The two proteins are 86% homologous. HSP86 was found to contain internal peptide repeats of Glu-Lys-Glu within a region of highly charged amino acid residues. The coding regions of the cDNAs were 76% homologous; however, this homology did not extend to the 5'- and 3'-untranslated regions. The 5'-untranslated region of hsp86 cDNA was considerably longer than that of hsp84 cDNA and, unlike that of hsp84, contained extraneous ATG triplets. Hsp86-related sequences were assigned to chromosomes 12, 11, and 3. An evolutionary tree constructed from HSP90-related protein sequences indicated that HSP86 and HSP84 were likely to have diverged more than 500 million years ago. The findings presented herein suggest that HSP86 and HSP84 may have different functions.