期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：26
页码：15469-15474
DOI：10.1073/pnas.2536698100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：During transcription elongation, RNA polymerase (RNAP) occasionally loses its grip on the growing RNA end and backtracks on the DNA template. Prokaryotic Gre factors rescue the backtracked ternary elongating complex through stimulation of an intrinsic endonuclease activity, which removes the disengaged 3' RNA segment. By using RNA-protein crosslinking in defined ternary elongating complexes, site-directed mutagenesis, discriminative biochemical assays, and docking of the two protein structures, we show that Gre acts by providing two carboxylate residues for coordination of catalytic Mg2+ ion in the RNAP active center. A similar mechanism is suggested for the functionally analogous eukaryotic SII factor. The results expand the general two-metal model of RNAP catalytic mechanism whereby one of the Mg2+ ions is permanently retained, whereas the other is recruited ad hoc by an auxiliary factor.
