Also found in: Dictionary, Encyclopedia, Wikipedia.
Related to sigma factor: RNA polymerase, TATA box
a factor that inhibits the nonspecific DNA binding of RNA polymerase, as well as helping to identify the starting point of transcription; it promotes attachment of the RNA polymerase to specific initiation sites.
Synonym(s): σ factor
A protein component of bacterial RNA polymerase that recognizes the correct site on DNA for initiating transcription of a gene and that is usually released soon after transcription begins.