CEA, iRCM, F-91057 Evry Cedex, France.
Curr Opin Struct Biol. 2009 Dec;19(6):740-5. doi: 10.1016/j.sbi.2009.10.005. Epub 2009 Nov 4.
Recent advances in elucidating the structure of yeast Pol I and III are based on a combination of X-ray crystal analysis, electron microscopy and homology modelling. They allow a better comparison of the three eukaryotic nuclear RNA polymerases, underscoring the most obvious difference existing between the three enzymes, which lies in the existence of additional Pol-I-specific and Pol-III-specific subunits. Their location on the cognate RNA polymerases is now fairly well known, suggesting precise hypotheses as to their function in transcription during initiation, elongation, termination and/or reinitiation. Unexpectedly, even though Pol I and III, but not Pol II, have an intrinsic RNA cleavage activity, it was found that TFIIS Pol II cleavage stimulation factor also played a general role in Pol III transcription.
近年来，基于 X 射线晶体分析、电子显微镜和同源建模的方法，人们对酵母 Pol I 和 III 的结构有了更深入的了解。这些方法可以更好地比较三种真核核 RNA 聚合酶，突出了这三种酶之间最明显的区别，即存在额外的 Pol-I 特异性和 Pol-III 特异性亚基。这些亚基在相应的 RNA 聚合酶上的位置现在已经相当清楚，这为它们在起始、延伸、终止和/或重新起始过程中的转录功能提出了精确的假说。出乎意料的是，尽管 Pol I 和 III 而不是 Pol II 具有内在的 RNA 切割活性，但发现 TFIIS Pol II 切割刺激因子在 Pol III 转录中也发挥了普遍作用。
