Yoshinaga S K, Boulanger P A, Berk A J
Proc Natl Acad Sci U S A. 1987 Jun;84(11):3585-9. doi: 10.1073/pnas.84.11.3585.
tRNA genes and adenovirus viral-associated (VA) genes are transcribed by RNA polymerase III. Transcription of these genes in vitro requires two protein fractions containing transcription factors designated TFIIIB and TFIIIC, in addition to RNA polymerase III. We report that the TFIIIC fraction derived from human cells in culture can be separated into two functional components, which we call TFIIIC1 and TFIIIC2. Both TFIIIC1 and TFIIIC2 fractions are required for in vitro transcription of the VA1 gene. In DNase I "footprinting" experiments, the TFIIIC2 fraction protects the internal control region termed the B block. Addition of the TFIIIC1 fraction extends the footprint over the internal control region called the A block. TFIIIC1 activity is the limiting transcription factor activity required for VA1 transcription in the crude extract. TFIIIC2 activity sediments as a large component of approximately 18 S, while TFIIIC1 activity sediments at approximately 9 S. These data indicate that the two activities are unique components and when added together reconstitute TFIIIC activity.
转运RNA（tRNA）基因和腺病毒病毒相关（VA）基因由RNA聚合酶III转录。在体外，这些基因的转录除了需要RNA聚合酶III外，还需要两个含有转录因子TFIIIB和TFIIIC的蛋白质组分。我们报道，来源于培养的人细胞的TFIIIC组分可分离为两个功能成分，我们将其称为TFIIIC1和TFIIIC2。VA1基因的体外转录需要TFIIIC1和TFIIIC2两个组分。在DNA酶I “足迹”实验中，TFIIIC2组分保护称为B区的内部控制区域。添加TFIIIC1组分可将足迹扩展至称为A区的内部控制区域。TFIIIC1活性是粗提物中VA1转录所需的限制转录因子活性。TFIIIC2活性沉降为约18 S的大分子成分，而TFIIIC1活性沉降在约9 S。这些数据表明这两种活性是独特的成分，一起添加时可重构TFIIIC活性。
