title: Identification of the nuclear localization signal of SALL4B, a stem cell transcription factor.
abstract: SALL4B plays a critical role in maintaining the pluripotency of embryonic stem cells and hematopoietic stem cells. SALL4B primarily functions as a transcription factor, and, thus, its nuclear localization is paramount to its biological activities. To understand the structural basis by which SALL4B was transported and retained in the nucleus, we made a series of SALL4B constructs with deletions or point mutations. We found that K64R mutation resulted in a random distribution of SALL4B within the cell. An analysis of neighboring amino acid sequences revealed that (64)KRLR (67) in SALL4B matches exactly with the canonical nuclear localization signal (K-K/R-x-K/R). SALL4B fragment (a.a. 50-109) that contained KRLR was sufficient for targeting GFP-tagged SALL4B to the nucleus, whereas K64R mutation led to a random distribution of GFP-SALL4B signal within the cell. We further demonstrated that the nuclear localization was essential for transactivating luciferase reporter gene driven by OCT4 promoter, a known transcriptional target of SALL4B. Therefore, our study identifies the KRLR sequence as a bona fide nuclear localization signal for SALL4B.
authors.affiliation: Biopharmaceutical Research Center; Chinese Academy of Medical Sciences & Peking Union Medical College; Suzhou, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wu
authors.affiliation: Department of Environmental Medicine; New York University Langone Medical Center; Tuxedo, NY USA.
authors.forename: Feikun
authors.initials: F
authors.lastname: Yang
authors.affiliation: Biopharmaceutical Research Center; Chinese Academy of Medical Sciences & Peking Union Medical College; Suzhou, China.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Ren
authors.affiliation: Biopharmaceutical Research Center; Chinese Academy of Medical Sciences & Peking Union Medical College; Suzhou, China.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Pathology; The State University of New York at Stony Brook; Stony Brook, NY USA.
authors.forename: Yupo
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Center for Drug Discovery; Northeastern University; Boston, MA USA and Sahlgrenska Academy; Gothenburg University; Gothenburg, Sweden.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Environmental Medicine; New York University Langone Medical Center; Tuxedo, NY USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D021381:Protein Transport; D013234:Stem Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D019913:Nuclear Localization Signals; C472575:SALL4 protein, human; D014157:Transcription Factors
keywords: SALL4B; nuclear localization; stem cells; transcription factor