# Chm7 and Heh1 form a nuclear envelope subdomain for nuclear pore complex quality control

## TL;DR

This study identifies a nuclear envelope subdomain formed by Chm7 and Heh1 that ensures proper nuclear pore complex assembly and prevents defects.

## Contribution

The discovery of a Heh1-dependent Chm7 recruitment pathway as a key component of nuclear pore complex quality control.

## Key findings

- Heh1 and Heh2 bind ESCRT-III Snf7 and ESCRT-II/III Chm7 in their open forms.
- Chm7 accumulates on the nuclear envelope when nuclear pore complex assembly is blocked.
- CHM7 deletion suppresses improper NPC compartment formation in vps4Δ strains.

## Abstract

Mechanisms that ensure the integrity of the nuclear envelope rely on membrane remodeling proteins like the ESCRTs and the AAA ATPase Vps4, which help seal the nuclear envelope at the end of mitosis and prevent the formation of defective nuclear pore complexes (NPCs). Here, we show that the integral inner nuclear membrane proteins Heh1 and Heh2 directly bind the ESCRT-III, Snf7, and the ESCRT-II/III chimera, Chm7, in their ‘open’ forms. Moreover, Heh1 is required for Chm7-recruitment to the nuclear envelope. As Chm7 accumulates on the nuclear envelope upon blocks to NPC assembly, but not to nuclear transport, interactions between ESCRTs and the Heh proteins might form a biochemically distinct nuclear envelope subdomain that delimits regions of assembling NPCs. Interestingly, deletion of CHM7 suppresses the formation of the storage of improperly assembled NPC compartment prevalent in vps4Δ strains. Thus, our data support that the Heh1-dependent recruitment of Chm7 is a key component of a quality control pathway whose local regulation by Vps4 and the transmembrane nup, Pom152, prevents loss of nuclear compartmentalization by defective NPCs.