Promoters

Promoters are regions of DNA upstream of genes that direct transcription initiation. They serve as binding sites for RNA polymerase and transcription factors, determine the transcription start site and directional transcription, and influence expression levels. Promoters vary across organisms and gene types.

In bacteria, promoters are recognized by the RNA polymerase holoenzyme together with a sigma factor. Core elements include the -35 and -10 regions, with typical sequences such as TTGACA and TATAAT, separated by about 17 nucleotides. Promoter strength is modulated by sequence context and regulatory proteins that respond to signals.

In eukaryotes, promoters are more diverse and often work with distal elements. A core promoter around the transcription start site may include a TATA box or be TATA-less but contain initiator elements. Proximal promoter elements such as CAAT or GC boxes regulate initiation and tissue-specific expression. Many genes use alternative promoters to generate different transcripts. Chromatin context, including DNA methylation and histone marks, shapes promoter accessibility and activity.

Mutation or epigenetic changes at promoters can alter gene expression and contribute to disease, including cancer.

In everyday language, a promoter may be a person or organization that arranges and publicizes events or markets a product or idea.