Molecular Biology Institute; Departments of Biology.
Molecular Biology Institute; Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030.
J Biol Chem. 2013 Sep 20;288(38):27564-27570. doi: 10.1074/jbc.C113.503094. Epub 2013 Aug 16.
In the fruit fly Drosophila melanogaster, RNA polymerase III transcription was found to be dependent not upon the canonical TATA box-binding protein (TBP) but instead upon the TBP-related factor 1 (TRF1) (Takada, S., Lis, J. T., Zhou, S., and Tjian, R. (2000) Cell 101, 459-469). Here we confirm that transcription of fly tRNA genes requires TRF1. However, we unexpectedly find that U6 snRNA gene promoters are occupied primarily by TBP in cells and that knockdown of TBP, but not TRF1, inhibits U6 transcription in cells. Moreover, U6 transcription in vitro effectively utilizes TBP, whereas TBP cannot substitute for TRF1 to promote tRNA transcription in vitro. Thus, in fruit flies, different classes of RNA polymerase III promoters differentially utilize TBP and TRF1 for the initiation of transcription.
在果蝇 Drosophila melanogaster 中，发现 RNA 聚合酶 III 的转录不依赖于经典的 TATA 盒结合蛋白 (TBP)，而是依赖于 TBP 相关因子 1 (TRF1)（Takada，S.，Lis，J. T.，Zhou，S.，和 Tjian，R.（2000）Cell 101，459-469）。在这里，我们证实了果蝇 tRNA 基因的转录需要 TRF1。然而，我们出人意料地发现，U6 snRNA 基因启动子在细胞中主要被 TBP 占据，并且 TBP 的敲低而非 TRF1 的敲低抑制了细胞中的 U6 转录。此外，U6 在体外转录有效地利用了 TBP，而 TBP 不能替代 TRF1 在体外促进 tRNA 转录。因此，在果蝇中，不同类别的 RNA 聚合酶 III 启动子在转录起始时差异地利用 TBP 和 TRF1。
