Molecular Mechanisms of C11orf95 translocations in cancer.

Highly recurrent chromosome translocations that produce oncogenic fusions are a prime example of practical therapeutic targets translating into clinical successes. We have previously described the genetic driver of supratentorial (forebrain) ependymomas as translocations of the C11orf95 gene of unknown function and RELA, the canonical nuclear effector of NF-B signalling. Subsequent studies have reinforced our original findings on the frequency (>70%) of these C11orf95-RELA (C11-RELA) fusions in human disease, as well as their transformative potential in multiple murine models. However, the mechanisms by which C11-RELA fusions transform neural stem cells into ependymomas remain elusive. Using multi-OMICS methodologies, we show that oncogenic C11orf95 fusions co-opt spatiotemporally regulated transcriptional activators. We find that the Zinc Fingers (ZF) of C11orf95 promote nuclear translocation and a common unique transcriptional signature mediated by the trans-activation domains (TAD) of the fused c-terminal protein partner. Specifically, the ZF’s of C11orf95 direct DNA-binding (as shown with ChIP-seq) of the fused protein partner but does not appear to alter the c-terminal protein’s nuclear interactome (identified using qPLEX-RIME and IP-MS). We further show that canonical NF-kB DNA binding and dimerization, mediated by the Rel homology domain (RHD), are completely dispensable for C11-RELA fusion function in vitro and transformation of neural stem cells in vivo. We henceforth demonstrate that supratentorial ependymoma, which have been previously described as a RELA fusion diseases, are truly a C11orf95 fusion disease, with ZFs serving as a scaffold for transcriptional dysregulation. Our studies lay the architectural framework for a molecular roadmap into the heart of C11orf95 fusion disease, elucidating the biochemical mechanisms which furnish the capacity of these fusions to operate as single gene oncogenes, and henceforth providing potential avenues for therapeutic intervention in ependymoma.Cancer Research U