Keeping RNA away from DNA

Newly transcribed RNA represents a threat to genomic stability, say Xialu Li and James Manley (Columbia University, New York, NY). They find that, in metazoan cells, the threat is neutralized by a splicing factor that coats RNA as it it emerges from RNA polymerase.

The danger arises because nascent RNA can anneal to the template DNA strand, thus forming an R loop. The nontranscribed strand is left as a single strand, potentially susceptible to attack by nucleases.

Bacteria combat this tendency by tightly coupling translation to transcription. In eukaryotes, this is not an option as transcription and translation are nuclear and cytoplasmic, respectively.

Li and Manley did not set out to discover a genome-protective mechanism, but chanced upon it while studying ASF/SF2. The Columbia team put this splicing protein under the control of...