Any Process Involved in the Assembly of the RNA Polymerase Preinitiation Complex (pic) At the Core Promoter Region of a DNA Template Resulting in the Subsequent Synthesis of RNA From That Promoter. the Initiation Phase Includes Pic Assembly and the Formation of the First Few Bonds in the RNA Chain Including Abortive Initiation Which Occurs When the First Few Nucleotides Are Repeatedly Synthesized and Then Released. the Initiation Phase Ends Just Before and Does Not Include Promoter Clearance or Release Which Is the Transition Between the Initiation and Elongation Phases of Transcription.
Transcription Factor Activity Sequence Specific DNA Binding
Interacting Selectively and Non Covalently with a Specific DNA Sequence in Order to Modulate Transcription. the Transcription Factor May or May Not Also Interact Selectively with a Protein or Macromolecular Complex.
A Sigma Factor Is the Promoter Specificity Subunit of Eubacterial Type Multisubunit RNA Polymerases Those Whose Core Subunit Composition Is Often Described As Alpha(2) Beta Beta Prime. (this Type of Multisubunit RNA Polymerase Complex Is Known to Be Found in Eubacteria and Plant Plastids). Although Sigma Does Not Bind DNA On Its Own When Combined with the Core to Form the Holoenzyme This Binds Specifically to Promoter Sequences with the Sigma Factor Making Sequence Specific Contacts with the Promoter Elements. the Sigma Subunit Is Released From the Elongating Form of the Polymerase and Is Thus Free to Act Catalytically For Multiple RNA Polymerase Core Enzymes.