NOP53 undergoes liquid-liquid phase separation and promotes tumor radio-resistance

Abstract

Aberrant DNA damage response (DDR) axis remains the major molecular mechanism for tumor radio-resistance. We recently characterized liquid-liquid phase separation (LLPS) as an essential mechanism of DDR, and identified several key DDR factors as potential LLPS proteins, including nucleolar protein NOP53. In this study, we found that NOP53 formed highly concentrated droplets in vivo and in vitro, which had liquid-like properties including the fusion of adjacent condensates, rapid fluorescence recovery after photobleaching and the sensitivity to 1,6-hexanediol. Moreover, the intrinsically disordered region 1 (IDR1) is required for NOP53 phase separation. In addition, multivalent-arginine-rich linear motifs (M-R motifs), which are enriched in NOP53, were essential for its nucleolar localization, but were dispensable for the LLPS of NOP53. Functionally, NOP53 silencing diminished tumor cell growth, and significantly sensitized colorectal cancer (CRC) cells to radiotherapy. Mechanically, NOP53 negatively regulated p53 pathway in CRC cells treated with or without radiation. Importantly, data from clinical samples confirmed a correlation between NOP53 expression and tumor radio-resistance. Together, these results indicate an important role of NOP53 in radio-resistance, and provide a potential target for tumor radio-sensitization.

JunB condensation attenuates vascular endothelial damage under hyperglycemic condition

“…We discovered that the puncta formed by endogenous or exogenous JunB diffused when the cells were transferred from 37°C to 4°C and re-formed when transferred back to 37°C ( Figure 3D ; Supplementary Figure S3B ). By incubating HUVECs with alcohol 1,6-hexanediol, which is widely used to destroy LLPS condensates ( Duster et al., 2021 ; Shi et al., 2021 , 2022 ), we revealed that droplets of endogenous or exogenous JunB were dissolved, and drug wash out reversed this effect ( Figure 3E ; Supplementary Figure S3C ). Thus, the temperature shift and 1,6-hexanediol treatment assays elucidated that endogenous or exogenous JunB formed reversible puncta in the nucleus.…”

The Burgeoning Significance of Liquid-Liquid Phase Separation in the Pathogenesis and Therapeutics of Cancers

“…Additionally, the nucleolar protein53 (Nop53) is overexpressed in colorectal cancer and correlates with poor prognosis. Nop53 forms cohesions in the nucleolus and exhibits sensitivity to 1,6-hexanediol treatment 159 . It inhibits p53 activation and enhances radioresistance in colorectal cancer cells, making it a potential target for increasing radiosensitivity in cancer patients 159 .…”

“…Nop53 forms cohesions in the nucleolus and exhibits sensitivity to 1,6-hexanediol treatment 159 . It inhibits p53 activation and enhances radioresistance in colorectal cancer cells, making it a potential target for increasing radiosensitivity in cancer patients 159 . Moreover, DExD-box helicase 21 (DDX21), a notable RNA-binding protein, is highly expressed in colorectal cancer.…”

Phase separation in DNA double-strand break response

“…These proteins form liquid-like droplets at sites of DNA damage, which facilitate the recruitment and assembly of other repair factors. This spatial organization allows for efficient and coordinated repair of damaged DNA [ 36 , 37 ].…”