Regulation of nuclear import during differentiation; The IMP alpha gene family and spermatogenesis

Abstract

Access to nuclear genes in eukaryotes is provided by members of the importin (IMP) superfamily of proteins, which are of alpha- or beta-types, the best understood nuclear import pathway being mediated by a heterodimer of an IMP alpha and IMP beta1. IMP alpha recognises specific targeting signals on cargo proteins, while IMP beta1 mediates passage into, and release within, the nucleus by interacting with other components of the transport machinery, including the monomeric guanine nucleotide binding protein Ran. In this manner, hundreds of different proteins can be targeted specifically into the nucleus in a tightly regulated fashion. The IMP alpha gene family has expanded during evolution, wi..