Induces RNA cleavage activity in the RNA polymerase. Induces rapid cleavage of a stalled transcription elongation complex with a 2-nucleotide reduction at the 3' end of the nascent RNA. Truncated RNA is able to resume elongation. During transcription elongation it enhances processivity (PubMed:29203770). 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. TFS1 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 (By similarity). Binds 2 Zn(2+) ions. Interacts with RNA polymerase; probably competes with TFS4 for the same binding site. Has 2 zinc-ribbon domains (N-ZR and C-ZR); functionally important residues Asp-94 and Glu-95 are probably located at the tip of a domain that extends from C-ZR into the RNAP active site. The nature of these residues determines if the protein is involved in stalled transcript cleavage and thus activation (Asp and Glu residues in this protein, TFS1) or in RNAP inhibition (Lys residues in TFS4). Belongs to the archaeal RpoM/eukaryotic RPA12/RPB9/RPC11 RNA polymerase family.