Genomic organization and chromosomal localization of the importin alpha1 gene in the mouse

Importin alpha1 (also referred to as NPI1 or importin alphaS1) gene encodes a member of the cytosolic receptor protein superfamily that recognizes classical monopartite and bipartite basic type nuclear localization signals and mediates nuclear protein import via an importin beta-dependent pathway. Here we report on the organization of the importin alpha1 locus in the mouse genome. The gene is approximately 40 kb in length from the translation initiation codon to the poly(A) additional site. The translated region of the gene is comprised of 13 coding exons and the exon-intron boundaries conform to the GT/AG rule. Importin alpha1 was mapped to a middle region of mouse chromosome 16 by fluorescence in situ hybridization analysis. Moreover, it was found by reverse transcriptase polymerase chain reaction analysis that importin alpha1 is widely expressed in various tissues in adult mice and at various stages during embyogenesis. This study is the first example that provides detailed genomic information on nuclear transport factors such as importins and exportins and provides a basis for further studies such as the generation of mutants in mice for purposes of investigating the role of importin alpha1 in development and differentiation.