BRCA1-Dependent Translational Regulation in Breast Cancer Cells

Estelle Dacheux,Nicole Dalla Venezia,Sylvie Mazoyer,Jean-Jacques Diaz,Anne Vincent,Christophe Combet,Anne Wierinckx,Joël Lachuer,Nicolas Nazaret,Philip J Tofilon

doi:10.1371/journal.pone.0067313

Abstract

BRCA1 (Breast Cancer 1) has been implicated in a number of cellular processes, including transcription regulation, DNA damage repair and protein ubiquitination. We previously demonstrated that BRCA1 interacts with PABP1 (Poly(A)-Binding Protein 1) and that BRCA1 modulates protein synthesis through this interaction. To identify the mRNAs that are translationally regulated by BRCA1, we used a microarray analysis of polysome-bound mRNAs in BRCA1-depleted and non-depleted MCF7 cells. Our findings show that BRCA1 modifies the translational efficiency of approximately 7% of the mRNAs expressed in these cells. Further analysis revealed that several processes contributing to cell surveillance such as cell cycle arrest, cell death, cellular growth and proliferation, DNA repair and gene expression, are largely enriched for the mRNAs whose translation is impacted by BRCA1. The BRCA1-dependent translation of these species of mRNAs therefore uncovers a novel mechanism through which BRCA1 exerts its onco-suppressive role. In addition, the BRCA1-dependent translation of mRNAs participating in unexpected functions such as cellular movement, nucleic acid metabolism or protein trafficking is indicative of novel functions for BRCA1. Finally, this study contributes to the identification of several markers associated with BRCA1 deficiency and to the discovery of new potential anti-neoplastic therapeutic targets.

Highlights

Loss of function of the tumour suppressor BRCA1 (Breast Cancer 1) protein is responsible for numerous familial and sporadic breast cancers
We have used a microarray analysis of polysomeassociated mRNA from BRCA1-depleted MCF7 cells to provide a genome-wide overview of the role played by BRCA1 in translational regulation
We calculated the relative translatability through the RR ratio (RR = polysomal RNA (polyRNA)/total cytoplasmic mRNA (totRNA)) to reveal, for each mRNA, the change in its association with polysomes independently to any change in its total cytoplasmic amount

Summary

Introduction

Loss of function of the tumour suppressor BRCA1 (Breast Cancer 1) protein is responsible for numerous familial and sporadic breast cancers. BRCA1 inactivating mutations are found in 8–10% of patients with familial breast cancer [1]. BRCA1 mutations are rare in sporadic cancers [2]. Sporadic breast cancers represent up to 90% of breast cancers and are often characterized by decreased BRCA1 expression at mRNA and protein levels [3] [4] [5]. BRCA1 interacts with the RNA polymerase II holoenzyme complex in part through binding to RNA helicase A, and interacts with the repair protein RAD51 or the ubiquitin ligase BARD1. The capacity of BRCA1 to form multiple protein complexes contributes to its central role in cell surveillance. Further studies are needed to fully appreciate the molecular mechanisms underlying the role of BRCA1 as a tumour suppressor

Methods

Results

Conclusion