A mutation in a promoter sequence most directly affects the binding of what to dna

RNA polymerase

Explanation:

The RNA polymerase is an enzyme used in the transcription of genes in DNA to make mRNA. RNA polymerase binds on the promoter region based on the sequences that can be identified by the enzyme's active site. A mutation can distort the interaction between the promoter region and the enzyme's active site hence throttle up or inhibit transcription.