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The nuclear import of transcription regulatory proteins appears to be used by the cell to trigger transitions in cell cycle, morphogenesis, and transformation. We have previously observed that the rate at which SV-40 T antigen fusion proteins containing a functional nuclear localization sequence (NLS; residues 126-132) are imported into the nucleus is enhanced in the presence of the casein kinase II (CK-II) site S111/112. In this study purified p34cdc2 kinase was used to phosphorylate T antigen proteins specifically at T124 and kinetic measurements at the single-cell level performed to assess its effect on nuclear protein import. T124 phosphorylation, which could be functionally simulated by a T-to-D124 substitution, was found to reduce the maximal extent of nuclear accumulation whilst negligibly affecting the import rate. The inhibition of nuclear import depended on the stoichiometry of phosphorylation. T124 and S111/112 could be phosphorylated independently of one another. Two alternative mechanisms were considered to explain the inhibition of nuclear import by T124 phosphorylation: inactivation of the NLS and cytoplasmic retention, respectively. Furthermore, we speculate that in vivo T124 phosphorylation may regulate the small but functionally significant amount of cytoplasmic SV-40 T antigen. A sequence comparison showed that many transcription regulatory proteins contain domains comprising potential CK-II-sites, cdc2-sites, and NLS. This raises the possibility that the three elements represent a functional unit regulating nuclear protein import.
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
April 1983,
Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
November 1993,
Oncogene,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
January 2010,
Bioorganicheskaia khimiia,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
January 2009,
Chemical biology & drug design,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
May 1967,
Virology,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
November 1996,
FEBS letters,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
September 1997,
The Journal of cell biology,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
October 2002,
Molecular and cellular biology,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
June 1987,
Experimental cell research,
D A Jans, and
M J Ackermann, and
J R Bischoff, and
D H Beach, and
R Peters
January 1975,
Biulleten' eksperimental'noi biologii i meditsiny,
