ACTIN-RELATED PROTEIN8 encodes an F-box protein localized to the nucleolus in Arabidopsis

Arabidopsis encodes six nuclear actin-related proteins (ARPs), among them ARP8 is unique in having an F-box domain and an actin homology domain. Analysis of the ARP8 promoter-beta-glucuronidase (GUS) fusion suggests that ARP8 is ubiquitously expressed in all organs and cell types. Immunocytochemical analysis with ARP8-specific monoclonal antibodies revealed that ARP8 protein is localized to the nucleolus in interphase cells and dispersed in the cytoplasm in mitotic cells. The cell cycle-dependent subcellular patterns of distribution of ARP8 are conserved in other members of Brassicaceae. Our findings provide the first insight into the possible contributions of plant ARP8 to nucleolar functions.