| In addition to interacting with AGP / EBP , Nopp 140 interacts specifically with TFIIB . ^^^ Distinct regions of Nopp 140 that interact with AGP / EBP and TFIIB have been characterized . ^^^ The sequence of Nopp 140 contains several stretches of serine and acidic amino acid rich sequences which are also found in ICP 4 of herpes simplex virus type 1 , a known transcription factor that interacts with TFIIB . ^^^ The physical interaction between TFIIB and wild type Nopp 140 or several deletion mutants of Nopp 140 correlates with the ability of Nopp 140 to activate the agp gene synergistically with AGP / EBP . ^^^ |