Abstract
The present study demonstrates different functional domains of a recently described centrosomal protein, Cep57 (centrosomal protein 57). Endogenous Cep57 protein and ectopic expression of full-length protein or the N-terminal coiled-coil domain localize to the centrosome internal to γ-tubulin, suggesting that it is either on both centrioles or on a centromatrix component. The N-terminus can also multimerize with the N-terminus of other Cep57 molecules. The C-terminus contains a second coiled-coil domain that directly binds to MTs (microtubules). This domain both nucleates and bundles MTs in vitro. This activity was also seen in vivo, as overexpression of full-length Cep57 or the C-terminus generates nocodazole-resistant MT cables in cells. Based on the present findings, we propose that Cep57 serves as a link with its N-terminus anchored to the centriole or centromatrix and its C-terminus to MTs.
- centriole
- centromatrix
- centrosomal protein 57 (Cep57)
- centrosome
- electron microscopy
- microtubule formation nucleation
Abbreviations: AKAP450, A-kinase-anchoring protein of 450 kDa; Cep57, centrosomal protein 57; Cep57R, Cep57-related protein; CLD, centrosome localization domain; CNN, centrosomin; Cy3, indocarbocyanine; DMEM, Dulbecco's modified Eagle's medium; DsRed, Discosoma corallimorpharian red fluorescent protein; EGF, epidermal growth factor; EM, electron microscopy; FBS, fetal bovine serum; GFP, green fluorescent protein; EGFP, enhanced GFP; GST, glutathione transferase; HEK-293 cells, human embryonic kidney-293 cells; hUbC, human ubiquitin C; JRed, a red fluorescent protein from a jellyfish of the suborder Anthomedusae; MT, microtubule; RNAi, RNA interference; SPD-5, spindle-defective protein-5
- © The Authors Journal compilation © 2008 Biochemical Society