A non-essential component of RNA polymerase (RNAP) (PubMed:6802805, PubMed:18289874, PubMed:21710567, PubMed:25092033). Has a similar structure to bacteriophage T7 protein Gp2 (AC P03704), which is known to bind to RNAP in the DNA binding-cleft. Unlike Gp2 however, this protein does not inhibit transcription initiation (PubMed:25092033). In vitro reconstitution experiments show this subunit is dispensible (PubMed:18289874). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Monomer (By similarity). RNAP is composed of a core of 2 alpha, a beta and a beta' subunit. The core is associated with a delta subunit, and at least one of epsilon or omega (PubMed:6802805, PubMed:18289874, PubMed:21710567, PubMed:25092033). When a sigma factor is associated with the core the holoenzyme is formed, which can initiate transcription (PubMed:18289874). Colocalizes with RNAP. Part of the rpoY-rnjA operon, transcribed constitutively. No visible phenotype; growth, bacterial fitness in competition experiments, RNAP distribution, global transcript levels and transcription initiation in vitro are all unaffected. Belongs to the RNA polymerase subunit epsilon family.