RNA-binding protein that suppresses transcription of some RNAs (PubMed:1703632, PubMed:9121479, PubMed:11027289, PubMed:15082769, PubMed:19687295, PubMed:26577379). Together with Wdr82, part of a transcription termination checkpoint that promotes transcription termination of RNAs and their subsequent degradation by the nuclear exosome (PubMed:26577379). Promotes transcription termination of aberrant RNAs, transcripts from genes containing a transposon inserted at their very 5' end or RNAs from heat-shock-inducible repetitive element (PubMed:1703632, PubMed:19687295, PubMed:26577379). Binds RNA preferentially at a sequence that resembles a cryptic 5'-splice site (PubMed:9121479). Interacts with Wdr82. Localizes to polytene chromosomes. At all stages. Belongs to the suppressor of sable family.