THE RCC1 PROTEIN INTERACTS WITH RAN, RANBP1, HSC70, AND A 340-KDA PROTEIN IN XENOPUS EXTRACTS

RCC1 is an abundant, highly conserved, chromatin-associated protein wh ose function is necessary for the preservation of a properly ordered c ell cycle, RCC1 is also necessary for numerous nuclear processes, incl uding nuclear transport and RNA metabolism; and it functions enzymatic ally as a guanine nucleotide exchange factor for a small, ras related GTPase called Ran. Studies in several organisms suggest that RCC1 may be part of a large complex containing multiple proteins. There is also evidence that RCC1 associates with chromatin through other proteins a nd that the binding of the complex to chromatin varies within the cell cycle. In order to characterize this putative complex, we have identi fied a number of other proteins as candidate compo nents of the comple x by their association with a GST-RCC1 fusion protein. Three of these proteins have previously been identified (Ran, RanBP1, and hsc70). The fourth protein is novel and has a molecular mass of 340 kDa. In this report, we discuss a preliminary characterization of the interactions between these proteins.