[Intact microtubule network is necessary for the EGF-induced transport of transcription factor STAT1 in the nucleus of A-431 cells].

The mechanism by which transcription factor STAT1 is translocated from the cytoplasm to the cell nucleus is not clear. We put forward a hypothesis suggesting an important role of the cytoskeleton in signal transduction. The results of the present work show that the treatment of cells with nocodazole, a microtubule-disrupting drug, inhibits completely STAT1 import to the nucleus. However, the treatment of cells with cytochalasin B, which is known to depolymerize microfilaments, exerted no detectable effect on the transport of STAT1. The sensitivity to nocodazole treatment suggests that STAT1 may utilize a transport pathway that involves the tubulin cytoskeleton. These data throw light on some mechanism of a rapid and effective nonvesicular transport of STAT1.