14-3-3 transits to the nucleus and participates in dynamic nucleocytoplasmic transport.
14-3-3 proteins regulate the cell cycle and prevent apoptosis by controlling the nuclear and cytoplasmic distribution of signaling molecules with which they interact. Although the majority of 14-3-3 molecules are present in the cytoplasm, we show here that in the absence of bound ligands 14-3-3 homes to the nucleus. We demonstrate that phosphorylation of one important 14-3-3 binding molecule, the transcription factor FKHRL1, at the 14-3-3 binding site occurs within the nucleus immediately before FKHRL1 relocalization to the cytoplasm. We show that the leucine-rich region within the COOH-terminal alpha-helix of 14-3-3, which had been proposed to function as a nuclear export signal (NES), instead functions globally in ligand binding and does not directly mediate nuclear transport. Efficient nuclear export of FKHRL1 requires both intrinsic NES sequences within FKHRL1 and phosphorylation/14-3-3 binding. Finally, we present evidence that phosphorylation/14-3-3 binding may also prevent FKHRL1 nuclear reimport. These results indicate that 14-3-3 can mediate the relocalization of nuclear ligands by several mechanisms that ensure complete sequestration of the bound 14-3-3 complex in the cytoplasm.
Brunet
Anne
A
Center for Cancer Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Kanai
Fumihiko
F
Stehn
Justine
J
Xu
Jian
J
Sarbassova
Dilara
D
Frangioni
John V
JV
Dalal
Sorab N
SN
DeCaprio
James A
JA
Greenberg
Michael E
ME
Yaffe
Michael B
MB
D048948:14-3-3 Proteins; D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
D048948:14-3-3 Proteins; D004268:DNA-Binding Proteins; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006133:Growth Substances; D028884:Karyopherins; D007930:Leucine; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D014446:Tyrosine 3-Monooxygenase; D000097606:Exportin 1 Protein; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human