Seminars

Plant responsiveness to light involves extensive changes in gene expression and histone marks across the genome that facilitate or not chromatin accessibility to transcriptional machineries. Both activities can be associated as transcription factor (TF)-based recruitment of chromatin modifiers in response to light has been reported in Arabidopsis. We have recently described a function for DET1, a repressor of photomorphogenesis, at the interface of TF association and chromatin regulation, where DET1 associates with E3 ubiquitin ligase COP1 in vivo, enhances COP1 interaction with TF HY5, and promotes HY5 destabilization. By regulating its accumulation, DET1 avoids HY5 association to hundreds of second-site genomic loci. The DET1-HY5 regulatory axis also involves a role for HY5 in controlling the H2Bub landscape. HY5 can directly interact with the H2Bub deubiquitination module (DUBm) and promotes stabilization of its SGF11 and UBP22 subunits, by dampening the interaction between DET1 complexes and SGF11. Accordingly, HY5 loss-of-function largely suppresses det1 chromatin defects by restoring wild-type H2Bub genomic profiles. Our findings indicate that a DET1-HY5 regulatory module has a general function of the epigenome landscape that goes beyond locus-specific regulation of light-regulated genes.

 

References:
Nassrallah A, Rougée M, Bourbousse C, Drevensek S, Fonseca S, Iniesto E, […], Bowler C, Rubio V*, Barneche F* (2018) DET1-mediated degradation of a SAGA- like deubiquitination module controls H2Bub homeostasis. eLIFE. e37892.
Cañibano E, Bourbousse C, Garcia-León M, […] Rubio V*, Fonseca S* (2021) DET1-mediated COP1 regulation avoids HY5 activity over second-site gene targets to tune plant photomorphogenesis. Molecular Plant 14:963-982.