Cloning of two novel human importin-α subunits and analysis of the expression pattern of the importin-α protein family

Abstract The import of many proteins into the nucleus is mediated by the importin-α/β heterodimer. While only one importin-β gene has been found, several forms of importin-α have been described. In addition to the three human importin-αs already identified, we report here the primary structure of two new human importin-αs proteins. The five known human importin-αs subunits can be classified into three subfamilies that appear conserved in higher eukaryotic organisms. We show by immunoblotting that the different importin-α subfamilies are expressed in a variety of human tissues and mammalian cell lines.