Title: Identification of the nuclear localization signal of SALL4B, a stem cell transcription factor.
Authors: Wu, Meng; Yang, Feikun; Ren, Zhihua; Jiang, Yongping; Ma, Yupo; Chen, Yan; Dai, Wei
Published In Cell Cycle, (2014)
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.
PubMed ID: 24626181
MeSH Terms: Amino Acid Sequence; Cell Nucleus/metabolism; HEK293 Cells; HeLa Cells; Humans; Molecular Sequence Data; Mutation; Nuclear Localization Signals*; Protein Transport; Stem Cells/metabolism*; Transcription Factors/genetics; Transcription Factors/metabolism*