Examining the involvement of Slx5 in the apoptotic response to chronic activation of the spindle assembly checkpoint.

Pınar Buket Atalay,Öykü Aşci,Elif Ergin Çavuşoğlu,Duygu Aygüneş

doi:10.3906/biy-1812-46

Abstract

Microtubule-targeting agents represent one of the most successful groups of anticancer drugs used in cancer therapy today. These drugs induce a prolonged mitotic arrest through chronic spindle assembly checkpoint (SAC) activation. Apoptosis, an outcome of the prolonged mitotic arrest, is the main mechanism by which these anticancer drugs kill cancer cells. However, not much is known about the mechanism that directs chronic SAC activation to apoptosis among other possible outcomes. The aim of this study is to investigate whether Slx5, a sumo-targeted ubiquitin E3 ligase, is involved in directing chronic SAC activation to apoptosis. We show that chronic SAC activation triggered by a 10-h nocodazole incubation leads to a prolonged mitotic arrest in the slx5Δ strain similar to wild type (WT). However, the proportion of cells displaying apoptotic features such as nuclear fragmentation, DNA fragmentation, and reactive oxygen species (ROS) production were increased more in the WT strain during the chronic SAC activation compared to slx5Δ, indicating that Slx5 may be involved in the chronic SAC-activation-apoptosis relation. We also showed that the possible role of Slx5 in the chronic SAC activation-apoptosis association was not through ubiquitin dependent degradation of 3 apoptosis-related and sumoylated candidate proteins.

Highlights

The spindle assembly checkpoint (SAC) is a conserved major cell cycle checkpoint, which ensures high fidelity of chromosome segregation in mitosis
We showed that the possible role of Slx5 in chronic SAC activation-apoptosis relation is not through ubiquitin dependent degradation of 3 apoptosis-related and sumoylated candidate proteins
Detection of the chronic SAC activation-dependent prolonged mitotic arrest In order to investigate whether slx5Δ cells display a SACdependent prolonged mitotic arrest in response to longterm treatment with nocodazole, an antimicrotubule drug,slx5Δ and wild type (WT) cells at early midlogarithmic phase were synchronized in G1 with and released into nocodazole containing medium for 10 h to trigger chronic SAC activation

Summary

Introduction

The spindle assembly checkpoint (SAC) is a conserved major cell cycle checkpoint, which ensures high fidelity of chromosome segregation in mitosis. Since SAC activation prevents cell proliferation by inducing a mitotic arrest in response to improper kinetochore-microtubule attachments, microtubules represent one of the most successful chemotherapeutic targets in clinic today. Two groups of anticancer drugs, taxanes (paclitaxel/taxol, docetaxel) and vinca alkaloids (vinblastine, vincristine) that are successfully used in the treatment of several types of cancer in clinic, prevent cancer proliferation by targeting microtubules (Hadfield et al, 2003; Marques et al, 2015). Both groups of drugs disrupt spindle microtubules, prevent proper attachments.

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