Structure of an RNA Polymerase II–TFIIB Complex and the Transcription Initiation Mechanism

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Science  08 Jan 2010:
Vol. 327, Issue 5962, pp. 206-209
DOI: 10.1126/science.1182015

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Previous x-ray crystal structures have given insight into the mechanism of transcription and the role of general transcription factors in the initiation of the process. A structure of an RNA polymerase II–general transcription factor TFIIB complex at 4.5 angstrom resolution revealed the amino-terminal region of TFIIB, including a loop termed the “B finger,” reaching into the active center of the polymerase where it may interact with both DNA and RNA, but this structure showed little of the carboxyl-terminal region. A new crystal structure of the same complex at 3.8 angstrom resolution obtained under different solution conditions is complementary with the previous one, revealing the carboxyl-terminal region of TFIIB, located above the polymerase active center cleft, but showing none of the B finger. In the new structure, the linker between the amino- and carboxyl-terminal regions can also be seen, snaking down from above the cleft toward the active center. The two structures, taken together with others previously obtained, dispel long-standing mysteries of the transcription initiation process.

  • * Present address: Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA.

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