Orlova M, Newlands J, Das A, Goldfarb A, Borukhov S
Public Health Research Institute, New York, NY 10016, USA.
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4596-600. doi: 10.1073/pnas.92.10.4596.
The GreA and GreB transcript cleavage factors of Escherichia coli suppress elongation arrest and may have a proofreading role in transcription. With the use of E. coli greA-greB- mutant, RNA polymerase is demonstrated to possess substantial intrinsic transcript cleavage activity. Mildly alkaline pH mimics the effect of the Gre proteins by inducing transcript cleavage in ternary complexes and antagonizing elongation arrest through a cleavage-and-restart reaction. Thus, transcript cleavage constitutes the second enzymological activity of RNA polymerase along with polymerization/pyrophosphorolysis of RNA, whereas the Gre proteins merely enhance this intrinsic property.
大肠杆菌的GreA和GreB转录物切割因子可抑制延伸停滞，并且可能在转录过程中具有校对作用。利用大肠杆菌greA - greB - 突变体，证明RNA聚合酶具有相当大的内在转录物切割活性。轻度碱性pH通过诱导三元复合物中的转录物切割并通过切割和重新启动反应拮抗延伸停滞，从而模拟Gre蛋白的作用。因此，转录物切割与RNA的聚合/焦磷酸解一起构成了RNA聚合酶的第二种酶学活性，而Gre蛋白只是增强了这种内在特性。
