A cytoplasmically anchored nuclear protein interferes specifically with the import of nuclear proteins but not U1 snRNA.
A cytoplasmically anchored mutant SV40 T antigen, FS T antigen, was shown previously to interfere specifically with the nuclear import of a heterologous nuclear protein, adenovirus 5 fiber protein, in cultured monkey cells (Schneider, J., C. Schindewolf, K. van Zee, and E. Fanning. 1988. Cell. 54:117-125; van Zee, K., F. Appel, and E. Fanning. 1991. Mol. Cell. Biol. 11:5137-5146). In this report, we demonstrate that FS T antigen also interferes with the nuclear import of adenovirus E1A and a peptide-albumin conjugate bearing multiple copies of the T antigen nuclear localization signal, but not with the import of U1 snRNA. A kinetic analysis indicates that nuclear import of the albumin-peptide conjugate is inhibited only when high intracellular concentrations of FS T antigen are reached. After microinjection into the cytoplasm of cultured cells, purified FS T antigen protein does not accumulate at the nuclear periphery, but rather is distributed in a punctate pattern throughout the cytoplasm. These data support a model in which cytoplasmic anchoring of FS T antigen enables the mutant protein to sequester and titrate out a cellular factor which is required for nuclear protein but not U1 snRNA import.
van Zee
K
K
Institut für Biochemie, Munich, Federal Republic of Germany.
Dickmanns
A
A
Fischer
U
U
Lührmann
R
R
Fanning
E
E
D017500:Adenovirus E1A Proteins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000032:analysis / Q000235:genetics / Q000494:pharmacology*; D002460:Cell Line / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism*; D014709:Vero Cells
D017500:Adenovirus E1A Proteins; D000957:Antigens, Viral, Tumor; D009687:Nuclear Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear