The KASH protein Kms2 coordinates mitotic remodeling of the spindle pole body

Abstract

Defects in the biogenesis of the spindle pole body (SPB), the yeast centrosome equivalent, can lead to monopolar spindles and mitotic catastrophe. The KASH domain protein Kms2 and SUN domain protein Sad1 colocalize within the nuclear envelope (NE) at the site of SPB attachment during interphase and at the spindle poles during mitosis in S. pombe. We show that Kms2 interacts with the essential SPB components Cut12 and Pcp1 and the Polo kinase, Plo1. Depletion of Kms2 delays mitotic entry and leads to defects in the insertion of the SPB into the NE, disrupting stable bipolar spindle formation. These effects are mediated in part by a delay in recruitment of Plo1 to the SPB at mitotic entry. Plo1 activity supports mitotic SPB remodeling by driving a burst of incorporation of Cut12 and Pcp1. Thus, a fission yeast SUN-KASH complex plays an important role in supporting remodeling of the SPB at mitotic entry.