Abstract

TenA (transcription enhancement) family proteins are widespread in bacteria, yet their functions in regulating natural product biosynthesis remain largely unexplored. Here, we report that LysR2, a TenA-family protein encoded by the lysolipin I biosynthetic gene cluster, acts as a transcriptional activator. Genetic and biochemical analyses reveal that LysR2 employs a noncanonical mechanism. Lacking a standard DNA-binding domain, it does not bind target promoters directly. Instead, LysR2 activates transcription by specifically binding to the pathway-specific repressor, LysR1. This protein–protein interaction displaces LysR1 from its cognate promoter, thereby derepressing the transcription of the biosynthetic gene cluster. Our work provides the first experimental evidence for a regulatory role of a TenA-family protein and elucidates a unique indirect activation mechanism that broadens the paradigm of transcriptional regulation in bacterial natural product biosynthesis.