Transcription Dynamics Prevent RNA-Mediated Genomic Instability through SRPK2-Dependent DDX23 Phosphorylation

Publication date: 10 January 2017
Source:Cell Reports, Volume 18, Issue 2
Author(s): Sreerama Chaitanya Sridhara, Sílvia Carvalho, Ana Rita Grosso, Lina Marcela Gallego-Paez, Maria Carmo-Fonseca, Sérgio Fernandes de Almeida
Genomic instability is frequently caused by nucleic acid structures termed R-loops that are formed during transcription. Despite their harmful potential, mechanisms that sense, signal, and suppress these structures remain elusive. Here, we report that oscillations in transcription dynamics are a major sensor of R-loops. We show that pausing of RNA polymerase II (RNA Pol II) initiates a signaling cascade whereby the serine/arginine protein kinase 2 (SRPK2) phosphorylates the DDX23 helicase, culminating in the suppression of R-loops. We show that in the absence of either SRPK2 or DDX23, accumulation of R-loops leads to massive genomic instability revealed by high levels of DNA double-strand breaks (DSBs). Importantly, we found DDX23 mutations in several cancers and detected homozygous deletions of the entire DDX23 locus in 10 (17%) adenoid cystic carcinoma (ACC) samples. Our results unravel molecular details of a link between transcription dynamics and RNA-mediated genomic instability that may play important roles in cancer development.

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Teaser

Sridhara et al. show that oscillations in RNA Pol II dynamics during transcription initiate a molecular pathway that prevents R-loops accumulation. Depletion of either SRPK2 or DDX23, as observed in adenoid cystic carcinoma, disrupts this pathway, leading to RNA-mediated genomic instability.


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