TINY T-ANTIGEN - AN AUTONOMOUS POLYOMAVIRUS T-ANTIGEN AMINO-TERMINAL DOMAIN

Three mRNAs from the murine polyomavirus early region encode the three well-characterized tumor antigens, We report the existence of a fourt h alternatively spliced mRNA which encodes a fourth tumor antigen, tin y T antigen, which comprises the amino-terminal domain common to all o f the T antigens but is extended by six unique amino acid residues, Th e amount of tiny T antigen in infected cells is small because of its s hort half-life. Tiny T antigen stimulates the ATPase activity of Hsc70 , most likely because of its DnaJ-like motif, The common amino-termina l domain may interface with chaperone complexes to assist the T antige ns in carrying out their diverse functions of replication, transcripti on, and transformation in the appropriate cellular compartments.