VP-16 (Herpes Simplex Virus Protein) (HSV) is a activator protein that binds to a enhancer region in a genome. It doesnt have its own DNA binding domain it recognises transcription factors such as Oct 1 and binds to it. It also has an activation domain which is rich in acidic residues. The activation domians function is to help the binding of TF11B to the transcription complex assembly to enable transcription of that gene to occur. If a mutation occurs in VP-16 then it will fail to attract TF11B to the complex assembly and transcription will not occur.