title: Karyopherin α 3 and karyopherin α 4 proteins mediate the nuclear import of methyl-CpG binding protein 2.
abstract: Methyl-CpG binding protein 2 (MeCP2) is a nuclear protein with important roles in regulating chromatin structure and gene expression, and mutations in MECP2 cause Rett syndrome (RTT). Within the MeCP2 protein sequence, the nuclear localization signal (NLS) is reported to reside between amino acids 255-271, and certain RTT-causing mutations overlap with the MeCP2 NLS, suggesting that they may alter nuclear localization. One such mutation, R270X, is predicted to interfere with the localization of MeCP2, but recent in vivo studies have demonstrated that this mutant remains entirely nuclear. To clarify the mechanism of MeCP2 nuclear import, we isolated proteins that interact with the NLS and identified karyopherin α 3 (KPNA3 or Kap-α3) and karyopherin α 4 (KPNA4 or Kap-α4) as key binding partners of MeCP2. MeCP2-R270X did not interact with KPNA4, consistent with a requirement for an intact NLS in this interaction. However, this mutant retains binding to KPNA3, accounting for the normal localization of MeCP2-R270X to the nucleus. These data provide a mechanism for MeCP2 nuclear import and have implications for the design of therapeutics aimed at modulating the function of MeCP2 in RTT patients.
authors.affiliation: From the Program in Developmental Biology, the Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030 Medical Scientist Training Program.
authors.forename: Steven Andrew
authors.initials: SA
authors.lastname: Baker
authors.affiliation: the Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030 Department of Molecular and Human Genetics and Howard Hughes Medical Institute.
authors.forename: Laura Marie
authors.initials: LM
authors.lastname: Lombardi
authors.affiliation: From the Program in Developmental Biology, the Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030 Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030 and hzoghbi@bcm.edu.
authors.forename: Huda Yahya
authors.initials: HY
authors.lastname: Zoghbi
mesh_terms: D021581:Active Transport, Cell Nucleus; D019943:Amino Acid Substitution; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism; D015518:Rett Syndrome / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D028901:alpha Karyopherins / Q000235:genetics / Q000378:metabolism*
chemical_list: C106306:KPNA3 protein, human; C106259:KPNA4 protein, human; C497392:MECP2 protein, human; D051783:Methyl-CpG-Binding Protein 2; D019913:Nuclear Localization Signals; D028901:alpha Karyopherins
keywords: DNA methylation; MeCP2; Rett syndrome; autism; epigenetics; genotype-phenotype; nuclear transport; nucleus