Cofactor D functions as a centrosomal protein and is required for the recruitment of the gamma-tubulin ring complex at centrosomes and organization of the mitotic spindle.
Microtubules are highly dynamic structures, composed of alpha/beta-tubulin heterodimers. Biosynthesis of the functional dimer involves the participation of several chaperones, termed cofactors A-E, that act on folding intermediates downstream of the cytosolic chaperonin CCT (1, 2). We show that cofactor D is also a centrosomal protein and that overexpression of either the full-length protein or either of two centrosome localization domains leads to the loss of anchoring of the gamma-tubulin ring complex and of nucleation of microtubule growth at centrosomes. In contrast, depletion of cofactor D by short interfering RNA results in mitotic spindle defects. Because none of these changes in cofactor D activity produced a change in the levels of alpha-or beta-tubulin, we conclude that these newly discovered functions for cofactor D are distinct from its previously described role in tubulin folding. Thus, we describe a new role for cofactor D at centrosomes that is important to its function in polymerization of tubulin and organization of the mitotic spindle.
Cunningham
Leslie A
LA
Department of Biochemistry and the Biochemistry, Cell, and Developmental Biology Program, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Kahn
Richard A
RA
D000818:Animals; D002417:Cattle; D018385:Centrosome / Q000378:metabolism* / Q000648:ultrastructure*; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D008861:Microsomes / Q000378:metabolism; D008954:Models, Biological; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism*
D034741:RNA, Small Interfering; D014404:Tubulin