Antisense-Mediated Transcript Knockdown Triggers Premature Transcription Termination.

Antisense oligonucleotides (ASOs) that trigger RNase-H-mediated cleavage are commonly used to knock down transcripts for experimental or therapeutic purposes. In particular, ASOs are frequently used to functionally interrogate long noncoding RNAs (lncRNAs) and discriminate lncRNA loci that produce functional RNAs from those whose activity is attributable to the act of transcription. Transcription termination is triggered by cleavage of nascent transcripts, generally during polyadenylation, resulting in degradation of the residual RNA polymerase II (Pol II)-associated RNA by XRN2 and dissociation of elongating Pol II. Here, we show that ASOs act upon nascent transcripts and, consequently, induce premature transcription termination downstream of the cleavage site in an XRN2-dependent manner. Targeting the transcript 3' end with ASOs, however, allows transcript knockdown while preserving Pol II association with the gene body. These results demonstrate that the effects of ASOs on transcription must be considered for appropriate experimental and therapeutic use of these reagents.