Dual roles of the Arabidopsis PEAT complex in histone H2A deubiquitination and H4K5 acetylation

Histone H2A monoubiquitination is associated with transcriptional repression and needs to be removed by deubiquitinases to facilitate gene transcription in eukaryotes. However, the deubiquitinase responsible for genome-wide H2A deubiquitination in plants has yet to be identified. We found that the previously identified PEAT (PWWP-EPCR-ARID-TRB) complex components interact with both the ubiquitin-specific protease UBP5 and the redundant histone acetyltransferases HAM1 and HAM2 (HAM1/2) and thereby form a larger version of PEAT complex in Arabidopsis thaliana. UBP5 functions as an H2A deubiquitinase in a nucleosome substrate-dependent manner in vitro and mediates H2A deubiquitination at the whole-genome level in vivo. HAM1/2 are shared subunits of the PEAT complex and the conserved NuA4 histone acetyltransferase complex and are responsible for histone H4K5 acetylation. Within the PEAT complex, the PWWP components (PWWP1, PWWP2 and PWWP3) directly interact with UBP5 and are necessary for UBP5-mediated H2A deubiquitination, while the EPCR components (EPCR1 and EPCR2) directly interact with HAM1/2 and are required for HAM1/2-mediated H4K5 acetylation. This study not only identifies dual roles of the PEAT complex in H2A deubiquitination and H4K5 acetylation but also illustrates how these processes collaborate at the whole-genome level to regulate transcription and development in plants.