An RNA polymerase used in transcription is an enzyme that synthesizes RNA from a DNA template. Unlike a replicating DNA polymerase, it can start a new strand without a pre-existing paired strand end; initiation still requires the appropriate DNA signals and associated machinery. See Alberts et al.: RNA polymerase and transcription initiation.
A protein that confers promoter-recognition specificity on a bacterial-type RNA polymerase. Plastid sigma factors can be nuclear encoded and imported.
A nuclear-encoded plastid sigma factor involved in activation of the psbD gene promoter in Arabidopsis thaliana.[ref]
An RNA polymerase that uses RNA as its template. In some RNA interference pathways it helps generate substrates for small-RNA production.
An RNA-dependent RNA polymerase contributing to double-stranded precursors for canonical RdDM small RNAs.
The eukaryotic polymerase responsible for transcription of protein-coding genes and several noncoding transcripts. Its C-terminal-domain phosphorylation state helps regulate elongation.
The Mediator complex is a multiprotein coactivator involved in coupling regulatory proteins to RNA-polymerase-II transcription. A requirement for mediator activity can be tested by removal and restoration in a reconstituted transcription system.
