Arabidopsis CRL4 Complexes: Surveying Chromatin States and Gene Expression

Abstract

CULLIN4 (CUL4) RING ligase (CRL4) complexes contain a CUL4 scaffold protein, associated to RBX1 and to DDB1 proteins and have traditionally been associated to protein degradation events. Through DDB1, these complexes can associate with numerous DCAF proteins, which directly interact with specific targets promoting their ubiquitination and subsequent degradation by the proteasome. A characteristic feature of the majority of DCAF proteins that associate with DDB1 is the presence of the DWD motif. DWD-containing proteins sum up to 85 in the plant model species Arabidopsis. In the last decade, numerous Arabidopsis DWD proteins have been studied and their molecular functions uncovered. Independently of whether their association with CRL4 has been confirmed or not, DWD proteins are often found as components of additional multimeric protein complexes that play key roles in essential nuclear events. For most of them, the significance of their complex partnership is still unexplored. Here, we summarize recent findings involving both confirmed and putative CRL4-associated DCAF proteins in regulating nuclei architecture remodelling, DNA damage repair, histone post-translational modification, mRNA processing and export, and ribosome biogenesis, that definitely have an impact in gene expression and de novo protein synthesis. We hypothesized that, by maintaining accurate levels of regulatory proteins through targeted degradation and transcriptional control, CRL4 complexes help to surveil nuclear processes essential for plant development and survival.

HOS15 is a transcriptional corepressor of NPR1-mediated gene activation of plant immunity

“…Taken together, we conclude that the corepressor HOS15 regulates the dynamic balance between transcriptional gene activation and repression in plant immunity by functioning as a substrate receptor in the E3 ubiquitin ligase complex that mediates degradation of the coactivator NPR1 to prevent target gene activation in unchallenged conditions and to limit activation during SA-mediated defense signaling. In Arabidopsis, three cullin-based E3 ubiquitin ligase complexes have been best characterized, CUL1-based ubiquitin ligase complex (SCF), CUL3-based ubiquitin ligase complex (BCR/ CLR3), and CUL4-based ubiquitin ligase complex (DCX/ CRL4) (69)(70)(71). Here, we have shown that HOS15 displays protein interactions consistent with its function as a substrate receptor for an SCF E3 ubiquitin ligase complex (SI Appendix, Figs.…”

Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis

“…Not well understood is the co-action of COP1 with DET1, another essential protein in the suppression of photomorphogenesis in darkness ( Pepper et al, 1994 ). DET1 associates with DDB1, COP10, and DDB1-ASSOCIATED 1 (DDA1) to form a COP10-DDB1-DET1-DDA1 (C3D) complex that binds CUL4 and functions as a CUL4-based E3 ligase ( Chen et al, 2006 ; Irigoyen et al, 2014 ; Fonseca and Rubio, 2019 ). Since Arabidopsis COP1 interacted with DDB1 independently of DET1, it was proposed that the CUL4-DDB1-COP1/SPA complex may be structurally distinct from the CUL4-C3D complex ( Chen et al, 2010 ; Lau and Deng, 2012 ; Irigoyen et al, 2014 ).…”

HD2-type histone deacetylases: unique regulators of plant development and stress responses

“…HOS15, a DDB1-CUL4 Associated factor (DCAF) protein, encodes one of 85 WD40-repeat proteins in Arabidopsis which directly interact with speci c targets by acting as a substrate receptor for its ubiquitination and subsequent degradation by the proteasome (Ali and Yun 2020;Fonseca and Rubio 2019). Zhu, et al (2008) reported the association of HOS15 with HD2C in histone modi cation in response to cold stress in Arabidopsis.…”