The yeast nuclear pore complex functionally interacts with components of the spindle assembly checkpoint

Abstract

Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p–Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.

Vertebrate Nup53 Interacts with the Nuclear Lamina and Is Required for the Assembly of a Nup93-containing Complex

“…In yeast, physical and genetic interactions have also been detected between Nup53p and the spindle checkpoint protein Mad1p (Iouk et al, 2002). Similarly, Mad1 is bound to the vertebrate NPC during interphase (Campbell et al, 2001).…”

“…The most welldefined function of Mad1 is its role in the spindle assembly checkpoint, a quality control feature of chromosome segregation that monitors spindle attachment to kinetochores during mitosis (reviewed in Lew and Burke, 2003). Intriguingly, Mad1 is localized to the NPC during interphase in both mammalian and yeast cells (Campbell et al, 2001;Iouk et al, 2002). However, it remains to be determined what function the association of Mad1 with the NPC plays in the spindle assembly checkpoint or to what degree Mad1 contributes to the function of the NPC.…”

The Entire Nup107-160 Complex, Including Three New Members, Is Targeted as One Entity to Kinetochores in Mitosis

“…Similarly, no detectable signal could be observed at kinetochores with GFP-Nup35. Such a signal could have been expected because the S. cerevisiae ortholog of this nucleoporin, Nup53, associate with Mad1 and Mad2 in yeast (Iouk et al, 2002), and vertebrates Mad1 localizes to kinetochores in mitosis (Campbell et al, 2001).…”

“…In particular, two metaphase checkpoint proteins that are transient components of kinetochores, Mad1 and Mad2, reportedly localize at nuclear pores in interphase both in vertebrates and yeasts (Campbell et al, 2001;Ikui et al, 2002;Iouk et al, 2002). In S. cerevisiae, Mad1 and Mad2 were shown to be associated with NPCs through the Nup53p subcomplex (Iouk et al, 2002).…”

“…In particular, two metaphase checkpoint proteins that are transient components of kinetochores, Mad1 and Mad2, reportedly localize at nuclear pores in interphase both in vertebrates and yeasts (Campbell et al, 2001;Ikui et al, 2002;Iouk et al, 2002). In S. cerevisiae, Mad1 and Mad2 were shown to be associated with NPCs through the Nup53p subcomplex (Iouk et al, 2002). In vertebrates, the WD (tryptophane-aspartic acid)-repeat-containing protein Rae1 (also called Gle2 or mrnp41) that interacts with the nucleoporin Nup98 (Pritchard et al, 1999) was shown to interact with the mitotic checkpoint protein mBUB1 and to be localized at kinetochores of prometaphase chromosomes (Wang et al, 2001).…”