Control of Gene Expression-Transcription Factors Transcription factors(TFS) are proteins that bind to the dna and help to control gene expression. We call the sequences to which they bind transcription factor binding sites(TFBSs), which are a type of CIS-regulatory sequence Department of Biochemistry Molecular Biology eDepartment of Biochemistry & Molecular Biology 3 Control of Gene Expression—Transcription Factors Transcription factors (TFs) are proteins that bind to the DNA and help to control gene expression. We call the sequences to which they bind transcription factor binding sites (TFBSs), which are a type of cis-regulatory sequence