Biology subjects

Ha, S. A.

Publications and source records attributed to Ha, S. A..

2 recordsLinked to original sources

bioRxiv2025

The MYCN/Aurora-A complex is a cyclin activating kinase for CDK12

Deregulated MYCN is a driver of aggressive pediatric and adult neuroendocrine tumors, but critical oncogenic processes downstream of MYCN remain poorly defined. In neuroblastoma, MYCN interacts with and activates the Aurora-A kinase. Here we show that Aurora-A is a CDK-activating kinase for CDK12 by phosphorylating T893 in the T-loop, thereby enhancing its kinase activity. Aurora-A-dependent activation of CDK12 controls phosphorylation of T4 of RNA polymerase and recruits transcription termination complexes, thereby preventing transcription-replication conflicts. Enhanced crosslinking and immunoprecipitation sequencing reveals that Aurora-A associates with splice sites on nascent RNA. RNA-bound Aurora-A is catalytically inactive. MYCN competes with RNA for binding to Aurora-A and displaces Aurora-A from RNA in cells, promoting its CDK12 kinase activity. Combining Aurora-A and CDK12 inhibition potently suppresses the growth of MYCN-amplified neuroblastoma cells and patient-derived xenografts. Our data demonstrate that an Aurora-A/CDK12-dependent transcription termination pathway is a critical and targetable dependency of MYCN-driven tumors.

cancer biology↗

bioRxiv2023

Direct RNA-binding by MYCN mediates feedback from RNA processing to transcription control

The MYCN oncoprotein broadly binds active promoters in a heterodimer with its partner protein MAX. MYCN also interacts with the nuclear exosome, a 3-5 exoribonuclease complex, suggesting a function in RNA metabolism. Here we show that MYCN forms stable high molecular weight complexes with the exosome and multiple RNA-binding proteins. In cells, MYCN binds to thousands of intronic RNAs; recombinant MYCN directly binds RNA via a short, highly conserved sequence termed MYCBoxI. Perturbing exosome function results in global re-localization of MYCN from promoters to intronic RNAs. At promoters, MYCN is then replaced by the MNT(MXD6) repressor protein, which inhibits MYCN-dependent transcription. MYCN promotes the degradation of its bound introns via the nuclear exosome targeting (NEXT) complex. Our data demonstrate that MYCN is an RNA-binding protein that regulates nascent transcript turnover and show that competition between its RNA- and DNA-bound states links the dynamics of the MYCN/MAX/MXD network to mRNA processing.

cancer biology↗