No abstract

The small ubiquitin-related modifier (SUMO) system is essential for smooth progression of cell cycle at the G2/M phase. Many centromeric proteins are reversibly SUMOylated to ensure proper chromosome segregation at the mitosis. SUMOylation of centromeric Origin Recognition Complex subunit 2 (ORC2) at the G2/M phase is essential in maintaining genome integrity. However, how ORC2 SUMOylation is regulated remains largely unclear. Here we show that ORC2 SUMOylation is reversibly controlled by SUMO E3 ligase PIAS4 and De-SUMOylase SENP2. Either depletion of PIAS4 or overexpression of SENP2 eliminated SUMOylation of ORC2 at the G/M phase and consequently resulted in abnormal centromeric histone H3 lysine 4 methylation. Cells stably expressing SENP2 protein or small interfering RNA for PIAS4 bypassed mitosis and endoreduplicated their genome to become polyploidy. Furthermore, percentage of polyploid cells is reduced after coexpression of ORC2-SUMO2 fusion protein. Thus, the proper regulation of ORC2 SUMOylation at the G2/M phase by PIAS4 and SENP2 is critical for smooth progression of the mitotic cycle of cells.

Objectives Dermatomyositis (DM) and clinically amyopathic dermatomyositis (CADM) patients with positive expression of anti-transcription intermediary factor 1-γ (anti-TIF1-γ) antibody (Ab) are characterized by distinct clinicopathological features. We aimed to determine the role of cytokine/chemokine profiles in the classification of anti-TIF1-γ positive DM/CADM patients. Methods Serum levels of 24 cytokines/chemokines were measured in 27 anti-TIF1-γ positive DM/CADM patients by a Luminex 200 system. Principal components analysis (PCA) and unsupervised hierarchical clustering were used to reduce variables and establish patient subgroups. Spearman’s correlation coefficient was calculated between cytokine/chemokine levels and disease activity markers. Results Among anti-TIF1-γ positive DM/CADM patients, two distinct patient clusters were identified. The diagnosis of CADM was more common in Cluster 1 than in Cluster 2 (58.3% vs 6.7%, p = 0.008). Skin disease activity was higher in Cluster 2 than in Cluster 1 as measured by CDASI-A (38.6 ± 10.4 vs 25.3 ± 10.0, p = 0.003). Patients within Cluster 2 exhibited significant muscle weakness (MRC ≤ 3, 33.3% vs 0.0%, p = 0.047), higher levels of anti-TIF1-γ Ab (92.4 ± 20.6 vs 66.9 ± 13.9, p = 0.001), and an increased malignancy rate (73.3% vs 25.0%, p = 0.021). Cluster 2 exhibited higher serum levels of CXCL10 (564.2 ± 258.8 vs 122.0 ± 97.8, p < 0.001), CCL2 (1136.6 ± 545.4 vs 441.6 ± 163.3, p < 0.001), Galectin-9 (38879.6 ± 20009.3 vs 12612.4 ± 6640.0, p < 0.001), IL-18 (436.1 ± 188.9 vs 243.0 ± 114.5, p = 0.003), TNF-α (9.3 ± 3.8 vs 5.6 ± 2.4, p = 0.007), and TNFRI (1385.1 ± 338.2 vs 2605.6 ± 928.5, p < 0.001) than Cluster 1. Conclusion In anti-TIF1-γ positive DM/CADM, we identified a “skin-predominant” cluster and a “hyperinflammation” cluster based on the cytokine/chemokine profiles. Cytokine/chemokine profiles in anti-TIF1-γ positive DM/CADM can identify discrete clusters of patients with different disease patterns, organ involvements, and clinical outcomes.