RNA polymerase II-associated protein (RAP) 74 binds transcription factor (TF) IIB and
blocks TFIIB-RAP30 binding. 

Fang SM; Burton ZF 

Department of Biochemistry, Michigan State University, East Lansing 48824, USA. 

J Biol Chem 271: 11703-9 (1996) 

Abstract

A set of deletion mutants of human RNA polymerase II-associated protein (RAP) 30, the small
subunit of transcription factor IIF (TFIIF; RAP30/74), was constructed to map functional
domains. Mutants were tested for accurate transcriptional activity, RAP74 binding, and TFIIB
binding. Transcription assays indicate the importance of both N- and C-terminal sequences for
RAP30 function. RAP74 binds to the N-terminal region of RAP30 between amino acids 1 and 98.
TFIIB binds to an overlapping region of RAP30, localized to amino acids 1-176 (amino acids
27-152 comprise a minimal binding region). The C-terminal region of RAP74 (amino acids
358-517) binds directly and independently to TFIIB. Interestingly, RAP74 blocks TFIIB-RAP30
binding, both by binding TFIIB and by binding RAP30. When the TFIIF complex is intact,
therefore, TFIIB-TFIIF contact is maintained through RAP74. If the TFIIB-RAP30 interaction is
physiologically important, the TFIIF complex must dissociate within some transcription
complexes.