Crystal structure of GCN5 PCAF N-terminal domain reveals atypical ubiquitin ligase structure
- J Biol Chem. 2020 Oct 23;295(43):14630-14639. doi: 10.1074/jbc.RA120.013431.
- 1. Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
- 2. Department of Molecular Metabolic Regulation, Diabetes Research Center, Research Institute, National Center for Global Health and Medicine, Shinjyuku-ku, Tokyo, Japan.
- 3. Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan.
- 4. Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan. Electronic address: [email protected].
General control nonderepressible 5 (GCN5, also known as Kat2a) and p300/CBP-associated factor (PCAF, also known as Kat2b) are two homologous acetyltransferases. Both proteins share similar domain architecture consisting of a PCAF N-terminal (PCAF_N) domain, acetyltransferase domain, and a bromodomain. PCAF also acts as a ubiquitin E3 Ligase whose activity is attributable to the PCAF_N domain, but its structural aspects are largely unknown. Here, we demonstrated that GCN5 exhibited ubiquitination activity in a similar manner to PCAF and its activity was supported by the ubiquitin-conjugating enzyme UbcH5. Moreover, we determined the crystal structure of the PCAF_N domain at 1.8 Å resolution and found that PCAF_N domain folds into a helical structure with a characteristic binuclear zinc region, which was not predicted from sequence analyses. The zinc region is distinct from known E3 Ligase structures, suggesting this region may form a new class of E3 Ligase. Our biochemical and structural study provides new insight into not only the functional significance of GCN5 but also into ubiquitin biology.