Another role for cargo proteins

The kinesin proteins (KIFs) are "cargo" proteins that transport vesicles, protein complexes, and RNA to specific destinations in a cell, but their direct involvement in more discrete activities such as transcription has been unclear. In the December 20 Science, Betina Macho and colleagues at the Institut de Genetique et de Biologie Moleculaire et Cellulaire, Strasbourg, France, show that a kinesin directly controls the activity of a transcriptional coactivator by a tight regulation of its intracellular localization (Science, 298:2388-2390, December 20, 2002).

Macho et al. observed that in murine male germ cells kinesin KIF17b associates selectively with ACT — a transcriptional activator regulating various postmeiotic genes. The ACT-KIF17b interaction directly determined the intracellular localization of ACT and was restricted to specific stages of spermatogenesis. In addition, they showed that KIF17b could be actively exported from the nucleus through the Crm1 receptor.

"The findings presented here expand the...