A Mad2-Mediated Translational Regulatory Mechanism Promoting S-Phase Cyclin Synthesis Controls Origin Firing and Survival to Replication Stress

Cell survival to replication stress depends on the activation of the Mec1ATR-Rad53 checkpoint response that protects the integrity of stalled forks and controls the origin firing program. Here we found that Mad2, a member of the spindle assembly checkpoint (SAC), contributes to efficient origin firing and to cell survival in response to replication stress. We show that Rad53 and Mad2 promote S-phase cyclin expression through different mechanisms: while Rad53 influences Clb5,6 degradation, Mad2 promotes their protein synthesis. We found that Mad2 co-sediments with polysomes and modulates the association of the translation inhibitor Caf204E-BP with the translation machinery and the initiation factor eIF4E. This Mad2-dependent translational regulatory process does not depend on other SAC proteins. Altogether our observations indicate that Mad2 has an additional function outside of mitosis to control DNA synthesis and collaborates with the Mec1-Rad53 regulatory axis to allow cell survival in response to replication stress. [Display omitted] •Mad2 promotes origin firing in rad53 defective cells upon replication stress•Rad53 inhibits Clb5 degradation, while Mad2 promotes Clb5 synthesis•Mad2 inhibits Caf204E-BP by modulating its interaction with the translation machinery•The role of Mad2 in translation does not depend on other SAC proteins Here, Gay et al. show that, in addition to its well-established role in the spindle checkpoint, Mad2 promotes translation of S-phase cyclin mRNAs. This S-phase role of Mad2 is critical for cell survival following replication stress.