ABSTRACT
Zinc is an important trace element in the human body, and its homeostasis is closely related to amyotrophic lateral sclerosis (ALS). Cytoplasmic FUS proteins from patients with ALS aggregate their important pathologic markers. Liquid-liquid phase separation (LLPS) of FUS can lead to its aggregation. However, whether and how zinc homeostasis affects the aggregation of disease-associated FUS proteins in the cytoplasm remains unclear. Here, we found that zinc ion enhances LLPS and promotes the aggregation in the cytoplasm for FUS protein. In the FUS, the cysteine of the zinc finger (ZnF), recognizes and binds to zinc ions, reducing droplet mobility and enhancing protein aggregation in the cytoplasm. The mutation of FUS cysteine disrupts the dynamic regulatory switch of zinc ions and ZnF, resulting in insensitivity to zinc ions. These results suggest that the dynamic regulation of LLPS by binding with zinc ions may be a widespread mechanism and provide a new understanding of neurological diseases such as ALS and other ZnF protein-related diseases.
Subject(s)
Amyotrophic Lateral Sclerosis , RNA-Binding Protein FUS , Humans , Amyotrophic Lateral Sclerosis/genetics , Amyotrophic Lateral Sclerosis/metabolism , Cysteine/genetics , Mutation , Phase Separation , RNA-Binding Protein FUS/chemistry , RNA-Binding Protein FUS/genetics , RNA-Binding Protein FUS/metabolism , Zinc/metabolism , Zinc Fingers , Protein AggregatesABSTRACT
Tripartite motif (TRIM) family proteins as E3-ligases participate in various biological processes. TRIM21, as the first autoantibody protein, has been found to be associated with autophagy. However, the role of TRIM21 engaging in autophagy is still unclear. In this study, TRIM21 forms significate puncta in the cytoplasm and undergoes liquid-liquid phase separation in vitro. Furthermore, we identify phase separation of the coiled-coil (CC) domain is essential for autophagosome to mediate autophagy-related protein recruited. These findings show that phase separation of the CC domain of TRIM21 promotes autophagosome to impact cell fate.
Subject(s)
Autophagy , Proteins , Autophagy/physiology , Protein Domains , Ubiquitin-Protein Ligases/metabolism , Tripartite Motif ProteinsABSTRACT
Circadian clock genes regulate cancer development and chemotherapy susceptibility. Accordingly, chronotherapy based on circadian phenotypes might be applied to improve therapeutic efficacy. In this study, we investigated whether the circadian clock gene Bmal1 inhibited tumor development and increased paclitaxel sensitivity in tongue squamous cell carcinoma (TSCC). Bmal1 expression was downregulated and its rhythmic pattern of expression was affected in TSCC samples and cell lines. Ectopic Bmal1 inhibited cell proliferation, migration and invasion in vitro, and tumor growth in mouse xenograft models of TSCC. After exposure to paclitaxel, Bmal1-overexpressing cells displayed a relative increase in apoptosis and were more susceptible to paclitaxel treatment in vivo Mechanistic investigations suggested a regulatory connection between Bmal1, TERT, and the oncogenic transcriptional repressor EZH2 (enhancer of zeste homolog 2), the recruitment of which to the TERT promoter increased paclitaxel-induced apoptosis and cell growth inhibition. Clinically, paclitaxel efficacy correlated positively with Bmal1 expression levels in TSCC. Overall, our results identified Bmal1 as a novel tumor suppressor gene that elevates the sensitivity of cancer cells to paclitaxel, with potential implications as a chronotherapy timing biomarker in TSCC. Cancer Res; 77(2); 532-44. ©2016 AACR.
