Oral Presentation ESA-SRB-AOTA 2019

Estrogen receptor alpha controls gene expression via translational offsetting in breast and prostate cancer (#59)

Julie Lorent 1 , Richard J Rebello 2 , Vincent van Hoef 1 , Mitchell Lawrence 2 , Krzysztof J Szkop 1 , Eric Kusnadi 3 , Baila Samreen 1 , Preetika Balanathan 2 , Karin Scharmann 4 , Itsuhiro Takizawa 2 , Sebastian A Leidel 4 , Gail Risbridger 2 , Ivan Topisirovic 5 , Ola Larsson 1 , Luc Furic 3
  1. Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
  2. Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia
  3. Peter MacCallum Cancer Centre, Melbourne, VIC, Australia
  4. Cells-in-Motion Cluster of Excellence, Max Planck Institute for Molecular Biomedicine, Munster, Germany
  5. Gerald Bronfman Department of Oncology, McGill University, Montreal, Qc, Canada

Estrogen receptor alpha (ERα) activity is associated with increased proliferation in hormone-dependent cancers. Studies aiming to understand the impact of ERα on cancer-associated phenotypes have largely been limited to its transcriptional activity. Here we demonstrate that ERα coordinates its transcriptional output with selective modulation of mRNA translation. Importantly, translational perturbations caused by depletion of ERα largely manifest as “translational offsetting” of the transcriptome, whereby amounts of translated mRNA and protein levels are maintained constant despite changes in mRNA abundance. Transcripts whose levels, but not polysome-association, are reduced following ERα depletion lack features which limit translational efficiency including structured 5’UTRs and miRNA target sites. In contrast, mRNAs induced upon ERα depletion whose polysome-association remains unaltered are enriched in codons requiring U34-modified tRNAs for efficient decoding. Consistently, ERα regulates levels of U34-modification enzymes, whereas altered expression of U34-modification enzymes disrupts ERα dependent translational offsetting.  Our preliminary data also show that ERα-dependent changes in U34-modifications may be associated with drug resistance and our findings therefore may have important implications in understanding alterations in gene expression programs following treatment with ERα antagonists. Altogether, we unravel a hitherto unprecedented mechanism of ERα-dependent orchestration of transcriptional and translational programs, and highlight that translational offsetting may be a pervasive mechanism of proteome maintenance in cancer. Furthermore, our results suggest that tRNA U34 modifications may be a common therapeutic vulnerability shared between hormone-dependent cancers.