Inactivation of ribosomal protein S27-like impairs DNA interstrand cross-link repair by destabilization of FANCD2 and FANCI

Siyuan Sun,Yuanyuan Ma,Jie Xu,Yi Sun,Xiufang Xiong,Hengqian He,Guoan Chen

doi:10.1038/s41419-020-03082-9

Abstract

Ribosomal protein S27-like (RPS27L), an evolutionarily conserved ribosomal protein and a direct p53 target, plays an important role in maintenance of genome integrity. We have previously reported that RPS27L regulates radiation sensitivity via the MDM2-p53 and MDM2-MRN-ATM axes. Whether and how RPS27L modulates DNA interstrand cross-link (ICL) repair is unknown. Here we identified that RPS27L binds to FANCD2 and FANCI, two Fanconi anemia (FA) proteins functioning in ICL repair pathway. Upon RPS27L knockdown, the levels of FANCD2 and FANCI are reduced due to accelerated degradation via p62-mediated autophagy-lysosome pathway, which is abrogated by chloroquine (CQ) treatment or Beclin 1 knockdown. Biologically, RPS27L knockdown suppresses FANCD2 foci formation and impairs ICL repair upon exposure to ICL-inducing agent mitomycin C (MMC) in lung cancer cells. This effect of MMC sensitization can be partially reversed by CQ treatment. Together, our study shows that RPS27L positively regulates ICL repair by binding with FANCD2 and FANCI to prevent their degradation via autophagy-lysosome system.

Highlights

DNA interstrand cross-links (ICLs), an extremely deleterious form of DNA lesions, are induced by widely used chemotherapeutic agents, such as mitomycin C (MMC), cisplatin, and psoralen, as well as by endogenous metabolic intermediates, such as aldehydes[1,2]
Ribosomal protein S27-like (RPS27L) interacts with FANCD2 and FANCI Our previous study suggested that RPS27L regulates radiation sensitivity in both p53-dependent and p53independent manners[13]
We performed co-immunoprecipitation experiments to verify the interaction between FANCD2/FANCI and RPS27L and found that ectopically expressed FLAG-RPS27L readily pulled down endogenous FANCD2 and FANCI (Fig. 1A)

Summary

Introduction

DNA interstrand cross-links (ICLs), an extremely deleterious form of DNA lesions, are induced by widely used chemotherapeutic agents, such as mitomycin C (MMC), cisplatin, and psoralen, as well as by endogenous metabolic intermediates, such as aldehydes[1,2]. Of 22 FA proteins, FANCD2 and FANCI, which form a heterodimer with each other, known as ID2 complex, appear to play a central role in the FA pathway to repair ICLs. ID2 complex is recruited to chromatin at DNA ICLs, where both FANCD2 and FANCI are monoubiquitylated by the FA core complex, consisting of multiple FA proteins (FANCA/B/C/E/F/G/L/M) and other FA-associated proteins[1]. The monoubiquitylated ID2 complex recruits downstream repair effectors, such as structure-specific nucleases, to unhook and excise the ICLs, and to eventually repair the ICLs6,7

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Results

Conclusion