An E3 ligase complex regulates SET-domain polycomb group protein activity in Arabidopsis thaliana

Abstract

Transcriptional repression via methylation of histone H3 lysine 27 (H3K27) by the polycomb repressive complex 2 (PRC2) is conserved in higher eukaryotes. The Arabidopsis PRC2 controls homeotic gene expression, flowering time, and gene imprinting. Although downstream target genes and the regulatory mechanism of PRC2 are well understood, much less is known about the significance of posttranslational regulation of PRC2 protein activity. Here, we show the posttranslational regulation of CURLY LEAF (CLF) SETdomain polycomb group (PcG) protein by the F-box protein, UP-WARD CURLY LEAF1 (UCL1). Overexpression of UCL1 generates mutant phenotypes similar to those observed in plants with a loss-of-function mutation in the CLF gene. Leaf curling and early flowering phenotypes of UCL1 overexpression mutants, like clf mutants, are rescued by mutations in the AGAMOUS and FLOWER-ING LOCUS T genes, which is consistent with UCL1 and CLF functioning in the same genetic pathway. Overexpression of UCL1 reduces the level of CLF protein and alters expression and H3K27 methylation of CLF-target genes in transgenic plants, suggesting that UCL1 negatively regulates CLF. Interaction of UCL1 with CLF was detected in plant nuclei and in the yeast two-hybrid system. The UCL1 F-box binds in vivo to components of the E3 ligase complex, which ubiquitylate proteins that are subsequently degraded via the ubiquitin-26S proteasome pathway. Taken together, these results demonstrate the posttranslational regulation of the CLF SET-domain PcG activity by the UCL1 F-box protein in the E3 ligase complex.histone methylation | proteasome | gene silencing | epigenetics | protein stability

The catalytic subunit ofArabidopsisDNA polymerase α ensures stable maintenance of histone modification

“…To analyze further the interaction between ICU2 and LHP1 in planta, a bimolecular fluorescence complementation (BiFC) assay was also performed using protoplasts from Arabidopsis mesophyll cells. Although the interaction between the F-box protein UCL1 and CLF was observed as previously reported (Jeong et al, 2011), we failed to detect any reconstituted YFP fluorescence from ICU2 and LHP1 reciprocal combinations in our experimental conditions (Fig. 5E).…”

“…BiFC analysis was performed as described previously (Jeong et al, 2011). Full-length cDNAs from ICU2 and LHP1 were reciprocally cloned into pSAT4-nEYFP-C1 and pSAT4-cEYFP-C1-B vectors containing the CaMV 35S promoter.…”

Wild tomato endosperm transcriptomes reveal common roles of genomic imprinting in both nuclear and cellular endosperm

“…We also identified a cluster of SCF‐related PEGs on chromosome 8. Via ubiquitination, the SCF complex controls cyclin concentration, which serves as a switch between cell‐cycle steps; it has a central role in plant development and appears to be highly conserved across species (Gray et al ., ; Kim et al ., ; Jeong et al ., ; Boycheva et al ., ). Our results indicate that ubiquitination might be intricately linked to imprinting, and that imprinted expression of specific SCF‐complex genes might be required for cell‐cycle control in the endosperm.…”

Floral Transcriptomes in Woodland Strawberry Uncover Developing Receptacle and Anther Gene Networks

“…6C). DUF295 family FBX proteins play diverse functions from posttranslational regulation of the Su(var)3-9, Enhancerof-zeste, and Trithorax (SET) domain polycomb group protein (Jeong et al, 2011) to regulating ascorbic acid biosynthesis (Zhang et al, 2009). While we do not yet know the function of these FBX genes in the stage 9 anther, this is an important observation that will form the basis of future functional studies.…”