A new era of studying p53-mediated transcription activation

Abstract

To prevent tumorigenesis, p53 stimulates transcription by facilitating the recruitment of the transcription machinery on target gene promoters. Cryo-Electron Microscopy studies on p53-bound RNA Polymerase II (Pol II) reveal that p53 structurally regulates Pol II to affect its DNA binding and elongation, providing new insights into p53-mediated transcriptional regulation.

Keywords: 3D structure; RNA polymerase II; cryo-electron microscopy; p53; transcription activation.

Figure 1.

The cryo-EM 3D structure of the p53/Pol II co-complex (∼11 Å) is shown in 3 different views. The prominent extra EM density between p53/Pol II and Pol II alone maps is defined as the p53 protein (highlighted in dark purple). Pol II is colored gold with canonical structural features of Pol II indicated. Dashed red circles in the center and right panels indicate the upstream entry and downstream DNA sites on Pol II respectively. The scale bar represents 60 Å.

Figure 2.

The formation of Pol II dimer in the presence of p53 (A) Five representative 2D class averages displaying different views of a p53/Pol II dimer are shown. The scale bar represents 60 Å. (B) A putative 3D model of a p53/Pol II dimer is proposed based upon the 2D class averages shown in (A) via 2D/3D projection analysis. The p53 EM density is highlighted in dark purple, while Pol II is colored gold. The scale bar represents 60 Å.

Figure 3.

A representative computational model of p53's multiplex interactions within the core PIC. Docking of our p53/Pol II cryo-EM structure into the atomic model of the human closed PIC (PIC, PDB: 5IYA) and the EM density of a TFIID/TFIIA/SCP promoter DNA complex (EMD: 3305) is shown. The EM density representing p53 is highlighted in dark purple while Pol II is colored gold. TBP, TFIIB and TFIIA are highlighted in red, dark blue, and orange respectively. TFIIE (dark red) and TFIIF (purple) are represented as ribbon structures for clarity. The EM density of TFIID is colored blue with Lobes B and C extending along an open surface of the PIC. This docking model implies that p53 likely contacts the TBP subunit (red) of TFIID, TFIIB (dark blue), and upstream promoter DNA (aqua) during p53/TFIID-mediated PIC assembly. The scale bar represents 60 Å.