Dual-function Spot 42 RNA encodes a 15-amino acid protein that regulates the CRP transcription factor

Dual-function RNAs base pair with target messenger RNAs as small regulatory RNAs and encode small protein regulators. However, only a limited number of these dual-function regulators have been identified. In this study, we show that a well-characterized base-pairing small RNA surprisingly also encodes a 15-amino acid protein. The very small protein binds the cyclic adenosine monophosphate receptor protein transcription factor to block activation of some promoters, raising the question of how many other transcription factors are modulated by unidentified small proteins.