The spindle pole body (SPB) provides microtubule-organizing functions in yeast and duplicates exactly once per cell cycle. The first step in SPB duplication is the half-bridge to bridge conversion via the antiparallel dimerization of the centrin (Cdc31)-binding protein Sfi1 in anaphase. The bridge, which is anchored to the old SPB on the proximal end, exposes free Sfi1 N-termini (N-Sfi1) at its distal end. These free N-Sfi1 promote in G1 the assembly of the daughter SPB (dSPB) in a yet unclear manner. This study shows that N-Sfi1 including the first three Cdc31 binding sites interacts with the SPB components Spc29 and Spc42, triggering the assembly of the dSPB. Cdc31 binding to N-Sfi1 promotes Spc29 recruitment and is essential for satellite formation. Furthermore, phosphorylation of N-Sfi1 has an inhibitory effect and delays dSPB biogenesis until G1. Taking these data together, we provide an understanding of the initial steps in SPB assembly and describe a new function of Cdc31 in the recruitment of dSPB components.
The N-terminus of Sfi1 and yeast centrin Cdc31 provide the assembly site for a new spindle pole body
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Diana Rüthnick, Jlenia Vitale, Annett Neuner, Elmar Schiebel; The N-terminus of Sfi1 and yeast centrin Cdc31 provide the assembly site for a new spindle pole body. J Cell Biol 1 March 2021; 220 (3): e202004196. doi: https://doi.org/10.1083/jcb.202004196
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