Tfb6, a previously unidentified subunit of the general transcription factor TFIIH, facilitates dissociation of Ssl2 helicase after transcription initiation.

Kenji Murakami, Brian J Gibbons, Ralph E Davis, Shigeki Nagai, Xin Liu, Philip J J Robinson, Tinghe Wu, Craig D Kaplan, Roger D Kornberg

Index: Proc. Natl. Acad. Sci. U. S. A. 109(13) , 4816-21, (2012)

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Abstract

General transcription factor TFIIH, previously described as a 10-subunit complex, is essential for transcription and DNA repair. An eleventh subunit now identified, termed Tfb6, exhibits 45% sequence similarity to human nuclear mRNA export factor 5. Tfb6 dissociates from TFIIH as a heterodimer with the Ssl2 subunit, a DNA helicase that drives promoter melting for the initiation of transcription. Tfb6 does not, however, dissociate Ssl2 from TFIIH in the context of a fully assembled transcription preinitiation complex. Our findings suggest a dynamic state of Ssl2, allowing its engagement in multiple cellular processes.