Exploring the Composition and Catalytic Specificity of Sorghum Histone Acetyltransferase Complexes

Histone acetylation plays important roles in gene regulation and is catalyzed by histone acetyltransferases (HATs). The performance of histone acetylation by HATs requires the involvement of other proteins to form multi-subunit complexes. The functions of three major HAT-containing complexes, namely SAGA, NuA4, and TFIID, have been extensively studied. Recently, the MEDIATOR complex was also found to be associated with HAT in Arabidopsis. However, these complexes have rarely been investigated in other plant species. In this study, we identify the subunits of four HAT-containing complexes in six different grass species by using Arabidopsis homologs as reference sequences. We then construct the phylogenetic trees to analyze their evolutionary relationships. The results indicate that all six grass species conserve all the subunits, despite gene duplication events occurring diversely in different species. Expression analysis shows that most of the genes encoding the subunits of the four HAT-containing complexes are constitutively expressed, with only low-level expression in pollen. Consistent with their cellular function, all four HATs are found to be localized in the nucleus in sorghum. Unlike their Arabidopsis counterparts, SbGCN5 specifically acetylates H3K4, H3K9, and H3K27, while SbMYST acetylates H4K5 and H4K12 in vitro. Additionally, we discover that SbTAF1 catalyzes acetylation of H3K9 and H4K5 for the first time. These findings provide valuable insights for further investigations into the function of HAT-containing complexes in grass species.