title: The nuclear localization signal of lymphoid enhancer factor-1 is recognized by two differentially expressed Srp1-nuclear localization sequence receptor proteins.
abstract: Proteins are directed to the nucleus by their nuclear localization sequences (NLSs) in a multistep process. The first step, which is to dock the NLS-containing protein to the nuclear pore, is carried out in part by a recently identified NLS receptor named Srp1/importin-alpha. Using the high mobility group (HMG) DNA binding domain of human lymphoid enhancer factor-1 (hLEF-1) as bait in a yeast two-hybrid screen, we have identified two different mouse Srp1 proteins (pendulin/importin-alpha and mSrp1) that each bind to a 9-amino acid sequence in hLEF-1 called the B box. We show that the B box of hLEF-1, a region essential for high affinity DNA binding, is also necessary and sufficient for nuclear localization, lending support to the model that NLSs can function both in nuclear transport and DNA binding. Pendulin and mSrp1 are the mouse homologues of hRch1/hSrp1alpha/importin-alpha and hSrp1/karyopherin alpha/NPI-1, respectively, and show considerable sequence divergence from each other. We find a surprising and significant difference in the expression pattern of pendulin and mSrp1 mRNA, suggesting that these two Srp1 proteins are distinguishable in function as well as sequence.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Irvine, 92717-4025, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Prieve
authors.forename: K L
authors.initials: KL
authors.lastname: Guttridge
authors.forename: J E
authors.initials: JE
authors.lastname: Munguia
authors.forename: M L
authors.initials: ML
authors.lastname: Waterman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D028884:Karyopherins; D051821:Lymphoid Enhancer-Binding Factor 1; D051379:Mice; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D009928:Organ Specificity; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D028901:alpha Karyopherins
chemical_list: D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D028884:Karyopherins; D051821:Lymphoid Enhancer-Binding Factor 1; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D028901:alpha Karyopherins; C094236:pendulin