NELF-E is recruited to DNA double-strand break sites to promote transcriptional repression and repair.

Double-strand breaks (DSBs) trigger rapid and transient transcription pause to prevent collisions between repair and transcription machineries at damage sites. Little is known about the mechanisms that ensure transcriptional block after DNA damage. Here, we reveal a novel role of the negative elongation factor NELF in blocking transcription activity nearby DSBs. We show that NELF-E and NELF-A are rapidly recruited to DSB sites. Furthermore, NELF-E recruitment and its repressive activity are both required for switching off transcription at DSBs. Remarkably, using I-SceI endonuclease and CRISPR-Cas9 systems, we observe that NELF-E is preferentially recruited, in a PARP1-dependent manner, to DSBs induced upstream of transcriptionally active rather than inactive genes. Moreover, the presence of RNA polymerase II is a prerequisite for the preferential recruitment of NELF-E to DNA break sites. Additionally, we demonstrate that NELF-E is required for intact repair of DSBs. Altogether, our data identify the NELF complex as a new component in the DNA damage response.