The rate of nuclear cytoplasmic protein transport is determined by the casein kinase II site flanking the nuclear localization sequence of the SV40 T-antigen.

摘要: We have previously demonstrated [Rihs, H.-P. and Peters, R. (1989) EMBO J., 8, 1479-1484] that the nuclear transport of recombinant proteins in which short fragments SV40 T-antigen are fused to amino terminus Escherichia coli beta-galactosidase is dependent on both localization sequence (NLS, residues 126-132) a phosphorylation-site-containing (T-antigen 111-125). While NLS determines specificity, rate controlled by sequence. The present study furthers this observation examines role various phosphorylation sites. Purified, fluorescently labeled were injected into cytoplasm Vero or hepatoma (HTC) cells kinetics measured laser microfluorimetry. By replacing serine threonine known be phosphorylated vivo, we identified casein kinase II (CK-II) site S111/S112 determining factor enhancement transport. Either 111 112 was sufficient elicit maximum enhancement. other sites (S120, S123, T124) had no influence rate. Examination literature suggested many harboring also contain putative CK-II at distance approximately 10-30 acid from NLS. has been implicated transmission growth signals nucleus. Our results suggest may exert controlling protein