Unique N-Terminal Interactions Connect F-BOX STRESS INDUCED (FBS) Proteins to a WD40 Repeat-like Protein Pathway in Arabidopsis

SCF-type E3 ubiquitin ligases provide specificity to numerous selective protein degradation events in plants, including those that enable survival under environmental stress. SCF complexes use F-box (FBX) proteins as interchangeable substrate adaptors to recruit protein targets for ubiquitylation. FBX proteins almost universally have structure with two domains: A conserved N-terminal F-box domain interacts with a SKP protein and connects the FBX protein to the core SCF complex, while a C-terminal domain interacts with the protein target and facilitates recruitment. The F-BOX STRESS INDUCED (FBS) subfamily of plant FBX proteins has an atypical structure, however, with a centrally located F-box domain and additional conserved regions at both the N- and C-termini. FBS proteins have been linked to environmental stress networks, but no ubiquitylation target(s) or biological function has been established for this subfamily. We have identified two WD40 repeat-like proteins in Arabidopsis that are highly conserved in plants and interact with FBS proteins, which we have named FBS INTERACTING PROTEINs (FBIPs). FBIPs interact exclusively with the N-terminus of FBS proteins, and this interaction occurs in the nucleus. FBS1 destabilizes FBIP1, consistent with FBIPs being ubiquitylation targets SCFFBS1 complexes. This work indicates that FBS proteins may function in stress-responsive nuclear events, and it identifies two WD40 repeat-like proteins as new tools with which to probe how an atypical SCF complex, SCFFBS, functions via FBX protein N-terminal interaction events.

WD40 repeat 43 mediates cell survival, proliferation, migration and invasion via vimentin in colorectal cancer

Background WD40 repeat (WDR)43 is an RNA-binding protein that belongs to the WDR domain protein family. Its biological function is largely unclear, particularly in colorectal cancer (CRC). Methods In the present study, we searched the TCGA database and found the correlation between WDR43 and CRC. Subsequently, the high expression of WDR43 in human clinical samples of CRC was validated and we further examined the biological functions of it in CRC cells. Finally, we explored potential downstream proteins or pathways and established subcutaneous xenograft model to verify our findings. Results Immunohistochemistry of 16 patient specimens confirmed that the expression of WDR43 was elevated in CRC. WDR43 knockdown was shown to increase apoptosis and inhibit the proliferation, migration and invasion of CRC cells in vitro and reduce tumorigenesis in animal models. In addition, it was found that WDR43 knockdown inhibited vimentin (VIM) expression in CRC cells and overexpression of VIM can partially reverse the effects of WDR43 both in vitro and in vivo. Conclusion In conclusion, the role of WDR43 in the occurrence and development of CRC was investigated in the present study. WDR43 may serve as a valuable biomarker and provide new options for the diagnosis and treatment of colorectal cancer.

Pathophysiological Significance of WDR62 and JNK Signaling in Human Diseases

The c-Jun N-terminal kinase (JNK) is highly evolutionarily conserved and plays important roles in a broad range of physiological and pathological processes. The WD40-repeat protein 62 (WDR62) is a scaffold protein that recruits different components of the JNK signaling pathway to regulate several human diseases including neurological disorders, infertility, and tumorigenesis. Recent studies revealed that WDR62 regulates the process of neural stem cell mitosis and germ cell meiosis through JNK signaling. In this review we summarize the roles of WDR62 and JNK signaling in neuronal and non-neuronal contexts and discuss how JNK-dependent signaling regulates both processes. WDR62 is involved in various human disorders via JNK signaling regulation, and may represent a promising therapeutic strategy for the treatment of related diseases.

Posttranslational regulation of FOXA1 by Polycomb and BUB3/USP7 deubiquitin complex in prostate cancer

Forkhead box protein A1 (FOXA1) is essential for androgen-dependent prostate cancer (PCa) growth. However, how FOXA1 levels are regulated remains elusive and its therapeutic targeting proven challenging. Here, we report FOXA1 as a nonhistone substrate of enhancer of zeste homolog 2 (EZH2), which methylates FOXA1 at lysine-295. This methylation is recognized by WD40 repeat protein BUB3, which subsequently recruits ubiquitin-specific protease 7 (USP7) to remove ubiquitination and enhance FOXA1 protein stability. They functionally converge in regulating cell cycle genes and promoting PCa growth. FOXA1 is a major therapeutic target of the inhibitors of EZH2 methyltransferase activities in PCa. FOXA1-driven PCa growth can be effectively mitigated by EZH2 enzymatic inhibitors, either alone or in combination with USP7 inhibitors. Together, our study reports EZH2-catalyzed methylation as a key mechanism to FOXA1 protein stability, which may be leveraged to enhance therapeutic targeting of PCa using enzymatic EZH2 inhibitors.

The Light-Induced WD40-Repeat Transcription Factor DcTTG1 Regulates Anthocyanin Biosynthesis in Dendrobium candidum

Dendrobium candidum is used as a traditional Chinese medicine and as a raw material in functional foods. D. candidum stems are green or red, and red stems are richer in anthocyanins. Light is an important environmental factor that induces anthocyanin accumulation in D. candidum. However, the underlying molecular mechanisms have not been fully unraveled. In this study, we exposed D. candidum seedlings to two different light intensities and found that strong light increased the anthocyanin content and the expression of genes involved in anthocyanin biosynthesis. Through transcriptome profiling and expression analysis, we identified a WD40-repeat transcription factor, DcTTG1, whose expression is induced by light. Yeast one-hybrid assays showed that DcTTG1 binds to the promoters of DcCHS2, DcCHI, DcF3H, and DcF3′H, and a transient GUS activity assay indicated that DcTTG1 can induce their expression. In addition, DcTTG1 complemented the anthocyanin deficiency phenotype of the Arabidopsis thaliana ttg1-13 mutant. Collectively, our results suggest that light promotes anthocyanin accumulation in D. candidum seedlings via the upregulation of DcTTG1, which induces anthocyanin synthesis-related gene expression.

Arabidopsis thaliana GTS1 transcripts are activated by yeast extract

WD40 repeat-containing proteins participate in DNA-protein and protein-protein interactions and positively regulate plant stress responses. GTS1, known as a WD40 repeat-containing protein, works as a scaffold protein and is important in ribosome biogenesis and also biomass accumulation. In this study, we evaluated the GIGANTUS1 (GTS1) gene expression in response to biotic and abiotic stress factors in Arabidopsis thaliana plants. In addition, we grew and characterized A. thaliana gts1 mutant (T-DNA SALK_010647) in order to observe the effects of its absence on plants. According to our results, 100-200 mM abscisic acid (ABA) and 100-200 mM sodium chloride (NaCl) treatment did not cause any changes in GTS1 gene expression, while only 6 h of 1 g/l and 2 g/l yeast extract (YE) treatment negatively affected GTS1 expression in 10-day-old plant explants. After 10 and 30 days of YE treatment, GTS1 gene expression was upregulated, and as a consequence plant growth efficiency was reduced. We thus concluded that through the downregulation of GTS1 transcripts, we could obtain better growth and/or higher biomass, which seems to be a good option for agricultural recruitments.