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‐α proteins. The five known human importin‐α 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.