Léveillard T, Kassavetis G A, Geiduschek E P
Department of Biology, University of California, San Diego, La Jolla 92093-0634.
J Biol Chem. 1993 Feb 15;268(5):3594-603.
Derivatives of the Saccharomyces cerevisiae SUP4 tRNATyr gene with binding sites for the transcription regulatory protein GCN4 located upstream of the transcriptional start site have been constructed. The effect of GCN4 on transcription of these genes by purified RNA polymerase III and transcription factors (TF) IIIB and IIIC has been analyzed. GCN4 effectively blocks initiation of transcription only when prebound to sites that overlap with the binding site of TFIIIB. Residual GCN4-repressed transcription is significantly redirected to nearby downstream sites, the selection of which depends on the location of bound GCN4. That prebound repressing GCN4 redirects, instead of merely blocking, the TFIIIC-dependent interaction of TFIIIB with DNA has been directly demonstrated by footprinting. The effect of GCN4 on transcription persists after it has been stripped off its DNA-binding site: once it has been redirected, DNA-bound TFIIIB remains in place, a consequence of the fact that it binds extraordinarily tightly to DNA without recognizing specific DNA sequence.
已构建出酿酒酵母SUP4 tRNATyr基因的衍生物，其转录起始位点上游具有转录调节蛋白GCN4的结合位点。分析了GCN4对这些基因由纯化的RNA聚合酶III以及转录因子IIIB和IIIC进行转录的影响。仅当GCN4预先结合到与TFIIIB结合位点重叠的位点时，它才会有效阻断转录起始。残留的GCN4抑制的转录会显著重定向到附近的下游位点，其选择取决于结合的GCN4的位置。通过足迹法已直接证明，预先结合的抑制性GCN4会重定向而不是仅仅阻断TFIIIB与DNA的TFIIIC依赖性相互作用。GCN4从其DNA结合位点被去除后，其对转录的影响仍然存在：一旦被重定向，结合在DNA上的TFIIIB会留在原位，这是因为它与DNA结合得异常紧密且不识别特定的DNA序列。
