Msc1 accumulates at and excludes nuclear pore complexes from nucleus-vacuole junctions.

Abstract

Msc1 is a yeast nuclear envelope (NE) protein that facilitates DNA double-strand break repair. In its absence, cells exhibit abnormal nuclear morphologies and maldistribution of nuclear pore complexes (NPCs). Msc1 is not uniformly distributed across the NE but concentrates onto dynamic patches that often coincide with blebs or herniations. Here, we report that Msc1 abundance and the number of patches dramatically increase after the diauxic shift. Msc1 patches are devoid of NPCs and fully colocalize with nucleus-vacuole junctions (NVJs), which are involved in piecemeal micronucleophagy. In the absence of Msc1, abnormal NPC aggregates accumulate adjacent to vacuoles, both at and outside the NE. We conclude that Msc1 is the key factor that maintains NPC homeostasis as cells prepare to enter quiescence.