14-3-3ε Boosts Bleomycin-induced DNA Damage
Response by Inhibiting the Drug-resistant Activity of MVP
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Abstract
Major
vault protein (MVP) is the predominant constituent of the
vault particle, the largest known ribonuclear protein complex. Although
emerging evidence have been establishing the links between MVP (vault)
and multidrug resistance (MDR), little is known regarding exactly
how the MDR activity of MVP is modulated during cellular response
to drug-induced DNA damage (DDR). Bleomycin (BLM), an anticancer drug,
induces DNA double-stranded breaks (DSBs) and consequently triggers
the cellular DDR. Due to its physiological implications in hepatocellular
carcinoma (HCC) and cell fate decision, 14-3-3ε was chosen as
the pathway-specific bait protein to identify the critical target(s)
responsible for HCC MDR. By using an LC–MS/MS-based proteomic
approach, MVP was first identified in the BLM-induced 14-3-3ε
interactome formed in HCC cells. Biological characterization revealed
that MVP possesses specific activity to promote the resistance to
the BLM-induced DDR. On the other hand, 14-3-3ε enhances BLM-induced
DDR by interacting with MVP. Mechanistic investigation further revealed
that 14-3-3ε, in a phosphorylation-dependent manner, binds to
the phosphorylated sites at both Thr52 and Ser864 of the monomer of
MVP. Consequently, the phosphorylation-dependent binding between 14-3-3ε
and MVP inhibits the drug-resistant activity of MVP for an enhanced
DDR to BLM treatment. Our findings provide an insight into the mechanism
underlying how the BLM-induced interaction between 14-3-3ε and
MVP modulates MDR, implicating novel strategy to overcome the chemotherapeutic
resistance through interfering specific protein–protein interactions