Emran Farida, Florens Laurence, Ma Beicong, Swanson Selene K, Washburn Michael P, Hernandez Nouria
Stony Brook University, Graduate Program in Molecular and Cellular Pharmacology, Stony Brook, NY 11794, USA.
Gene. 2006 Aug 1;377:96-108. doi: 10.1016/j.gene.2006.03.012. Epub 2006 May 20.
The RNA polymerase (pol) II and III human small nuclear RNA (snRNA) genes have very similar promoters and recruit a number of common factors. In particular, both types of promoters utilize the small nuclear RNA activating protein complex (SNAP(c)) and the TATA box binding protein (TBP) for basal transcription, and are activated by Oct-1. We find that SNAP(c) purified from cell lines expressing tagged SNAP(c) subunits is associated with Yin Yang-1 (YY1), a factor implicated in both activation and repression of transcription. Recombinant YY1 accelerates the binding of SNAP(c) to the proximal sequence element, its target within snRNA promoters. Moreover, it enhances the formation of a complex on the pol III U6 snRNA promoter containing all the factors (SNAP(c), TBP, TFIIB-related factor 2 (Brf2), and B double prime 1 (Bdp1)) that are sufficient to direct in vitro U6 transcription when complemented with purified pol III, as well as that of a subcomplex containing TBP, Brf2, and Bdp1. YY1 is found on both the RNA polymerase II U1 and the RNA polymerase III U6 promoters as determined by chromatin immunoprecipitations. Thus, YY1 represents a new factor that participates in transcription complexes formed on both pol II and III promoters.
RNA聚合酶（pol）II和III的人类小核RNA（snRNA）基因具有非常相似的启动子，并招募许多共同因子。特别是，这两种类型的启动子都利用小核RNA激活蛋白复合物（SNAP(c)）和TATA盒结合蛋白（TBP）进行基础转录，并由Oct-1激活。我们发现，从表达带标签的SNAP(c)亚基的细胞系中纯化的SNAP(c)与阴阳-1（YY1）相关，YY1是一种与转录激活和抑制都有关的因子。重组YY1加速了SNAP(c)与近端序列元件的结合，近端序列元件是其在snRNA启动子中的靶点。此外，它增强了在pol III U6 snRNA启动子上形成的复合物的形成，该复合物包含所有与纯化的pol III互补时足以指导体外U6转录的因子（SNAP(c)、TBP、TFIIB相关因子2（Brf2）和B双prime 1（Bdp1）），以及包含TBP、Brf2和Bdp1的亚复合物。通过染色质免疫沉淀确定，YY1存在于RNA聚合酶II的U1和RNA聚合酶III的U6启动子上。因此，YY1代表了一种新的因子，它参与在pol II和III启动子上形成的转录复合物。
