A 105 000 dalton antigen of transformed mouse cells is a stress protein

Antisera prepared in mice against syngeneic spontaneously transformed AL/N cells (anti-TAL/N serum) identified a number of protein antigens synthesized by simian virus 40 (SV40) transformed cells, among which was a protein with a molecular mass of 105 000 daltons (p105). Of these transformed cell antigens which were immunogenic in a syngeneic system, only p105 was detected in primary mouse kidney cell cultures. p105 isolated from normal and transformed mouse cells was demonstrated to be identical by two-dimensional gel analysis. Relatively small amounts of p105 were synthesized in quiescent primary cultures, while the protein was actively synthesized in SV40-infected as well as in proliferating mouse kidney cells, and its synthesis in quiescent cells could be induced by subjecting the cultures to glucose starvation or heat-shock treatment. Immunofluorescent staining and cellular fractionation showed that p105 is normally localized to cytoplasmic structures. The results suggest that the expression of p105 is intimately associated with the metabolic state of the cell.