Somesh Baggavalli P, Sigurdsson Stefan, Saeki Hideaki, Erdjument-Bromage Hediye, Tempst Paul, Svejstrup Jesper Q
Mechanisms of Transcription Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, UK.
Cell. 2007 Apr 6;129(1):57-68. doi: 10.1016/j.cell.2007.01.046.
Transcriptional arrest triggers ubiquitylation of RNA polymerase II (RNAPII). We mapped the yeast RNAPII ubiquitylation sites and found that they play an important role in elongation and the DNA-damage response. One site lies in a protein domain that is unordered in free RNAPII, but ordered in the elongating form, helping explain the preferential ubiquitylation of this form. The other site is >125 Angstroms away, yet mutation of either site affects ubiquitylation of the other, in vitro and in vivo. The basis for this remarkable coupling was uncovered: an Rsp5 (E3) dimer assembled on the RNAPII C-terminal domain (CTD). The ubiquitylation sites bind Ubc5 (E2), which in turn binds Rsp5 to allow modification. Evidence for folding of the CTD compatible with this mechanism of communication between distant sites is provided. These data reveal the specificity and mechanism of RNAPII ubiquitylation and demonstrate that E2s can play a crucial role in substrate recognition.
转录停滞会引发RNA聚合酶II（RNAPII）的泛素化。我们绘制了酵母RNAPII泛素化位点图谱，发现它们在延伸和DNA损伤反应中发挥重要作用。一个位点位于一个在游离RNAPII中无序但在延伸形式中有序的蛋白质结构域中，这有助于解释这种形式的优先泛素化。另一个位点距离超过125埃，但在体外和体内，任何一个位点的突变都会影响另一个位点的泛素化。这种显著偶联的基础被揭示：一个Rsp5（E3）二聚体组装在RNAPII C末端结构域（CTD）上。泛素化位点结合Ubc5（E2），而Ubc5又结合Rsp5以实现修饰。提供了与远距离位点之间这种通讯机制相兼容的CTD折叠证据。这些数据揭示了RNAPII泛素化的特异性和机制，并证明E2在底物识别中可以发挥关键作用。
