Rice Trithorax factor ULTRAPETALA 1 (OsULT1) specifically binds to “GAGAG” sequence motif present in Polycomb response elements

The Epigenetic Faces of ULTRAPETALA1

“…In fact, by in vitro assays, it has been shown that the SAND domain of human DEAF-1 (Deformed Epidermal Autoregulatory Factor-1) homolog recognizes the 5 -TTCG-3 sequence (Bottomley et al, 2001). This sequence differs from what has been reported in plants, where the SAND domain of recombinant OsULT1, has affinity for the 5 -GAGAG-3 sequence (Roy et al, 2019).…”

“…also contains a B-box motif (Figure 2A), a motif that seems to be important for protein-protein interaction (Torok and Etkin, 2001;Carles et al, 2005;Khanna et al, 2009). In the case of OsULT1 from Oryza sativa, it has been shown that is important for its multimerization (Roy et al, 2019). Meanwhile, the SAND domain has a DNA-binding function (Bottomley et al, 2001), and it is conserved in plants and animals in vast combinations with other protein domains on the Viridiplantae and metazoan lineages.…”

“…Furthermore, despite the lack of HMT activity of ULT1, it has been suggested that ult1 mutant plants have lower levels of H3K4me3 marks on AG and AP3 genes, which are associated with an increase of H3K27me3 PcG mark on these ULT1 targets (Carles and Fletcher, 2009;Pu et al, 2013), evidencing the ability of ULT1 to regulate these epigenetic marks. Interestingly, the 5 -GAGAG-3 Arabidopsis PRE motifs recognized by CLF and its functional homolog SWINGER (SWN), as well as by other core components of PcG (Deng et al, 2013;Xiao et al, 2017;Shu et al, 2019), can also be recognized by the OsULT1 SAND-domain (Roy et al, 2019). Given that the ULT1 SAND-domains from rice and Arabidopsis share 90.91% of similarity (Figure 2A), it could be predicted that Arabidopsis ULT1 can bind through its SAND domain to the same sites as PcG proteins and thereby interfere with H3K27me3 marks.…”

“…The Arabidopsis compass-like complex reported so far contains ATX1 as the H3K4me3 HMT (Jiang et al, 2009(Jiang et al, , 2011; however, there are other HMTs of H3K4, such as ATX1/SDG27, ATX2/SDG30, ATXR3/SDG2 and ATXR7/SDG25, that could form different COMPASS complexes (Sanchez et al, 2015). Indeed, it has been demonstrated that the SAND domain of OsULT1 is responsible for interacting with the SET-domain of OsTRX1, an ATX1 ortholog (Roy et al, 2019). The high similarity of Arabidopsis and rice SAND-domains of ULT1 (Figure 2A) suggests that ULT1 can also interact with different proteins with a SET-domain.…”

The Trithorax Group Factor ULTRAPETALA1 Regulates Developmental as Well as Biotic and Abiotic Stress Response Genes in Arabidopsis

“…These associations suggest that the ULT proteins may physically link sequence-specific TFs with histone methyltransferases and the transcription machinery. The UIF1, KAN1 and KAN2 TFs all bind to functional Polycomb response elements (Xiao et al 2017), and the rice OsULT1 protein itself directly binds a “GAGAG” motif present in Polycomb response elements (Roy et al 2019). Therefore the ULT proteins may play an important function in coordinating the specific placement of histone-modifying enzymes at target gene loci.…”