Identification of a novel member of mouse hsp70 family. Its association with cellular mortal phenotype.

A novel 66-kDa protein, named p66mot-1, is identified to be associated with cellular mortality by virtue of its presence in cytosolic fractions of serially passaged mouse embryonic fibroblasts (MEF) and the mortal hybrids obtained by the fusion of mortal (MEF) and immortal (MN48-1, derivative of NIH 3T3) cells. Immortal cells lack this protein in their cytosolic fractions. cDNA cloning and homology search placed it in the heat shock protein 70 (hsp70) family. Microinjection of anti-p66 antibody to senescent MEF could transiently stimulate their cell division, which supports the cellular mortality-related function of p66mot-1.