Dissecting transcription termination and RNA sorting in MYCN-driven tumors

The inherent stresses arising from oncogenic transcription can be counteracted by premature termination which removes RNA polymerase II (RNAPII) from DNA and enables the degradation of aberrant nascent RNA by the nuclear exosome.

When overexpressed, the MYCN oncoprotein fuels the growth of aggressive tumors by globally binding active promoters and invariably enhancing RNAPII transcription.

However, I have made two key discoveries showing that the function of MYCN is not restricted to gene activation: Firstly, MYCN interacts with the exosome and prevents conflicts of RNAPII with replication forks to avert lethal DNA damage.

Secondly, MYCN globally leaves promoters and directly binds nascent RNAs which are then steered to the exosome for decay.

RNA bound MYCN also forms large protein complexes comprising the ARS2 transcript sorting protein, RNAPII and termination factors.

These findings fundamentally expand MYCN function as they reveal that the oncoprotein exists in competing DNA- and RNA-bound states with the latter fulfilling a heretofore unknown RNA degrading role.In TerSor, we will investigate whether RNA-bound MYCN controls termination and RNA sorting processes to counteract aberrant transcription and thereby suppress DNA damage and immune recognition in neuroblastoma cells.

Firstly, we will map MYCN RNA-binding domains and test the effects of RNA-binding loss in cells and neuroblastoma mouse models. Secondly, we will explore MYCN-driven regulation of termination and RNA sorting machineries.

Thirdly, we will investigate how the exosome and MYCN mitigate DNA damage and the accumulation of immunogenic transcripts.

Finally, we will study the structure of MYCNs interface with exosome targeting complexes.Collectively, we will use cutting-edge approaches to profoundly further our understanding of MYCN oncogenic function by studying how the oncoproteins newly discovered ability to bind RNA maintains the genomic integrity and immune evasion of aggressive tumors.