title: Histone deacetylase 4 possesses intrinsic nuclear import and export signals.
abstract: Nucleocytoplasmic trafficking of histone deacetylase 4 (HDAC4) plays an important role in regulating its function, and binding of 14-3-3 proteins is necessary for its cytoplasmic retention. Here, we report the identification of nuclear import and export sequences of HDAC4. While its N-terminal 118 residues modulate the nuclear localization, residues 244 to 279 constitute an authentic, strong nuclear localization signal. Mutational analysis of this signal revealed that three arginine-lysine clusters are necessary for its nuclear import activity. As for nuclear export, leucine-rich sequences located in the middle part of HDAC4 do not function as nuclear export signals. By contrast, a hydrophobic motif (MXXLXVXV) located at the C-terminal end serves as a nuclear export signal that is necessary for cytoplasmic retention of HDAC4. This motif is required for CRM1-mediated nuclear export of HDAC4. Furthermore, binding of 14-3-3 proteins promotes cytoplasmic localization of HDAC4 by both inhibiting its nuclear import and stimulating its nuclear export. Unlike wild-type HDAC4, a point mutant with abrogated MEF2-binding ability remains cytoplasmic upon exogenous expression of MEF2C, supporting the notion that direct MEF2 binding targets HDAC4 to the nucleus. Therefore, HDAC4 possesses intrinsic nuclear import and export signals for its dynamic nucleocytoplasmic shuttling, and association with 14-3-3 and MEF2 proteins affects such shuttling and thus directs HDAC4 to the cytoplasm and the nucleus, respectively.
authors.affiliation: Molecular Oncology Group, Department of Medicine, Royal Victoria Hospital, McGill University Health Center, 687 Pine Avenue, Montréal, Quebec H3A 1A1, Canada.
authors.forename: A H
authors.initials: AH
authors.lastname: Wang
authors.forename: X J
authors.initials: XJ
authors.lastname: Yang
mesh_terms: D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002874:Chromosome Mapping; D004268:DNA-Binding Proteins / Q000378:metabolism; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D028884:Karyopherins; D007930:Leucine; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018006:Myogenic Regulatory Factors; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006655:Histone Deacetylases; D028884:Karyopherins; D007930:Leucine; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D014157:Transcription Factors; D000097606:Exportin 1 Protein; C578040:MEF2C protein, human; C578041:Mef2c protein, mouse; C400300:HDAC4 protein, human