CASEIN KINASE-II BINDS TO AND PHOSPHORYLATES CYTOPLASMIC DYNEIN

We have isolated a 27-kDa protein that hinds to cytoplasmic dynein. Mi crosequencing of a 17-amino acid peptide of this polypeptide yielded a sequence which completely matched the predicted sequence of the beta subunit of casein kinase II, a highly conserved serine/threonine kinas e. Affinity chromatography using a dynein column indicates that both t he alpha and beta subunits of casein kinase II are retained by the col umn from rat brain cytosol, Although dynactin is also bound to the col umn, casein kinase II is not a dynactin subunit, Casein kinase II does not co-immunoprecipitate with dynactin, and it binds to a dynein inte rmediate chain column which has been preblocked with excess p150(Glued ), a treatment that inhibits the binding of dynactin from cytosol. Bac terially expressed and purified rat dynein intermediate chain can be p hosphorylated by casein kinase II in vitro. Further, native cytoplasmi c dynein purified from rat brain can also be phosphorylated by casein kinase II in vitro. We propose that CKII may be involved in the regula tion of dynein function possibly by altering its cargo specificity or its ability to interact with dynactin.