Roles for regulators of cortical ER structure in maintaining NPC integrity

Abstract

The nuclear envelope (NE) and endoplasmic reticulum (ER) are components of the same contiguous membrane system with distinct functions. Mounting evidence indicates that some ER proteins have roles in nuclear pore complex (NPC) structure and function. Previously, we reported that reticulons and Yop1/DP1 play a role in the early steps of de novo NPC assembly. Here, we examined if Rtn1 and Yop1 are required for the insertion of spindle pole bodies (SPBs) of Saccharomyces cerevisiae. We propose that NPC and SPB biogenesis are altered in cells lacking Rtn1 and Yop1 due to competition between NPCs and SPBs for Ndc1, an essential assembly component of both complexes. We also identified NE roles for Lnp1 and Sey1, proteins required for proper cortical ER formation in S. cerevisiae. We characterized both genetic and physical interactions that link Lnp1 and Sey1 to the NPC. Together, our findings suggest that Lnp1’s role in NPC integrity is separable from functions in the ER and is linked to Ndc1 and Rtn1 interactions.