M phase phosphorylation of cytoplasmic dynein intermediate chain and p150(Glued)

To understand how the dramatic cell biological changes of oocyte maturation are brought about, we have begun to identify proteins whose phosphorylatio n state changes during Xenopus oocyte maturation. Here we have focused on o ne such protein, p83. We partially purified p83, obtained peptide sequence, and identified it as the intermediate chain of cytoplasmic dynein. During oocyte maturation, dynein intermediate chain became hyperphosphorylated at the time of germinal vesicle breakdown and remained hyperphosphorylated thr oughout the rest of meiosis and early embryogenesis. p150(Glued), a subunit of dynactin that has been shown to bind to dynein intermediate chain, unde rwent similar changes in its phosphorylation, Both dynein intermediate chai n and p150(Glued) also became hyperphosphorylated during M phase in XTC-2 c ells and HeLa cells. Thus, two components of the dynein-dynactin complex un dergo coordinated phosphorylation changes at two G(2)/M transitions (matura tion in oocytes and mitosis in cells in culture) but remain constitutively in their M phase forms during early embryogenesis. Dynein intermediate chai n and p150(Glued) phosphorylation may positively regulate mitotic processes , such as spindle assembly or orientation, or negatively regulate interphas e processes such as minus-end-directed organelle trafficking.