Identification of a new ADAR1-dependent RNA editing event in the cyclin dependent kinase CDK13 that promotes thyroid cancer cell hallmarks

Adenosine deaminases acting on RNA (ADAR) catalyze the conversion of adenosines into inosines (A-to-I), modifying a large proportion of cellular RNAs and associated with diverse cancers. We reported previously that ADAR1 is functionally important for thyroid cancer progression and A-to-I editing events are elevated in these tumors. However, the downstream effectors regulated or edited by ADAR1 and the significance of ADAR1 dysregulation in thyroid cancer remain unclear. Here we provide insight, by whole transcriptome sequencing, into the consequences of ADAR1 dysregulation on global gene expression, RNA splicing and RNA editing. Furthermore, we describe for the first time an oncogenic function for CDK13 in thyroid cancer and identified a new ADAR1-dependent RNA editing event that occurs in the coding region of its transcript. Moreover, CDK13 was significantly over-edited in tumor samples and our functional analysis revealed the importance of this specific editing event in promoting cancer cell hallmarks. Finally, we showed that the editing of CDK13 modifies its subcellular localization and that this event could explain, at least in part, the global change in splicing produced by ADAR1 dysregulation. In summary, our data reinforces A-to-I editing as an important pathway in cancer progression, identifying novel mechanisms that open new insights into future treatments in thyroid and other cancer types. Overall design: mRNA from Cal62 Thyroid cancer cells silenced for ADAR1 (#1 and #2) and siControl cells