Induces RNA cleavage activity in the RNA polymerase. In its presence, the cleavage activity of the RNA polymerase truncates the RNA back to position +15 in a stepwise manner by releasing mainly dinucleotides from the 3'-end of the nascent RNA. The truncated RNAs are able to continue elongation (PubMed:10777522). Involved in transcriptional proofreading and fidelity. Misincorporation of nucleotides during elongation of transcription leads to arrested elongation complexes which are rescued by TFS-promoted removal of a dinucleotide from the 3'-end. TFS is able to induce a cleavage resynthesis cycle in stalled elongation complexes (resulting from the next missing nucleotide or a reduced incorporation rate of a wrong nucleotide) preventing misincorporation and enabling proofreading in a post-incorporation manner. Pausing of elongation complexes is the main determinant of TFS-induced RNA cleavage (PubMed:15130130). Belongs to the archaeal RpoM/eukaryotic RPA12/RPB9/RPC11 RNA polymerase family. More similar by sequence similarity to the eukaryotic RNA polymerase subunits.