RNA-binding protein that suppresses transcription of long non-coding RNAs (lncRNAs) (PubMed:33913806, PubMed:33767452). LncRNAs are defined as transcripts more than 200 nucleotides that are not translated into protein (PubMed:33913806, PubMed:33767452). Together with WDR82, part of a transcription termination checkpoint that promotes transcription termination of lncRNAs and their subsequent degradation by the exosome (PubMed:33913806, PubMed:33767452). The transcription termination checkpoint is activated by the inefficiently spliced first exon of lncRNAs (PubMed:33767452). Interacts with WDR82. Recruited at sites of high RNA polymerase II occupancy. Belongs to the suppressor of sable family.