Mitotic checkpoint protein Mad1 is required for early Nup153 recruitment to chromatin and nuclear envelope integrity

Abstract

Nucleoporin Nup153 is a multifunctional protein and mitotic checkpoint protein Mad1 a known binding partner. The functional relevance of their interaction has remained elusive. Here, we have further dissected Nup153's and Mad1's interface and functional interplay. By in situ proximity ligation assays, we found that the presence of a nuclear envelope (NE) is prerequisite for the Nup153-Mad1 association. Time-lapse microscopy revealed that depletion of Mad1 delayed recruitment of Nup153 to anaphase chromatin, which was often accompanied by a prolongation of anaphase. Furthermore, as seen by electron microscopic and three-dimensional structured illumination investigations, Nup153 and Mad1 depletion led to alterations in NE architecture, characterised by a change of membrane curvature at nuclear pore complexes (NPCs) and an expansion of the spacing between inner and outer nuclear membrane. Nup153 depletion, but not of Mad1, caused defects in interphase NPC assembly with partial displacement of cytoplasmic nucleoporins and a reduction in NPC density. Together our results suggest that Nup153 has separable roles in NE and NPC formation: in post-mitotic NE reformation in concert with Mad1 and in interphase NPC assembly, independent of Mad1.

Yeast Fin1-PP1 dephosphorylates an Ipl1 substrate, Ndc80, to remove Bub1-Bub3 checkpoint proteins from the kinetochore during anaphase

“…Although strong kinetochore association of Bub1-Bub3 complex was noticed in cdc15-2 fin1Δ mutant cells in anaphase, no Mad1 was detected at the anaphase kinetochore in cdc15-2 fin1Δ or asynchronous fin1Δ anaphase cells (S2 Fig) . In these cells, Mad1 showed a characteristic nuclear envelop localization as described [28]. Thus, a distinct mechanism controls Mad1 kinetochore dissociation, which is likely the key to SAC silencing.…”

Cul3 substrate adaptor SPOP targets Nup153 for degradation

“…Many Nups have roles during cell division including the promotion of microtubule nucleation, regulation of the anaphase promoting complex/cyclosome, and localization of spindle assembly checkpoint proteins Mad1 and Mad2 (Mossaid and Fahrenkrog, 2015;Garcia et al, 2021). For example, during interphase, Nup153 is a nuclear pore complex protein in the nuclear basket that plays roles in nuclear trafficking (Ball and Ullman, 2005) and transcription (Toda et al, 2017), but during mitosis, Nup153 plays roles in nuclear pore complex assembly and nuclear envelope modeling (Duheron et al, 2014;Vollmer et al, 2015) and spindle assembly checkpoint regulation via an interaction with Mad1 (Lussi et al, 2010;Mossaid et al, 2020).…”

Phosphorylation of Mad1 at serine 18 by Mps1 is required for the full virulence of rice blast fungus, Magnaporthe oryzae

“…MoMad1 localizes on M. oryzae NE throughout the cell cycle, which is similar to its yeast homologue in the absence of spindle damage (Gillett et al., 2004 ; Scott et al., 2005 ). Mad1 proteins were found to regulate nuclear import in S. cerevisiae (Cairo et al., 2013 ), and engage in controlling NE architecture of human cells (Mossaid et al., 2020 ). These potential functions of MoMad1 beyond the SAC may be required for the full virulence of M. oryzae .…”