Dimerization of the centriolin-like protein Nud1 governs spindle pole body inheritance in budding yeast

Centrosome duplication is intrinsically asymmetric, creating an old and a new copy, and this difference is used to guide fate decisions during both proliferation and differentiation. The budding yeast centrosome equivalent, the spindle pole body (SPB), also duplicates asymmetrically. In yeast meiosis, this difference is used to coordinate the number of spores formed with the available carbon source. We report that the use of the older meiosis II SPBs to initiate spore formation requires a signal from acetate metabolism. This requirement is enforced by a homodimer of the Nud1 protein. Disruption of Nud1 dimerization abolishes age-dependent SPB behavior, while elevated Nud1 levels impair sporulation. We propose that dimers of Nud1 on the old SPB must be rearranged to allow meiosis-specific SPB proteins to bind and initiate spore formation. Nud1 dimerization also contributes to SPB asymmetry during mitosis, indicating that the Nud1 dimer is generally important for discriminating the age of the SPB.