Persistent infection with high-risk human papillomaviruses (HPVs), notably HPV-16 and HPV-18, underlies most cervical cancers and many head and neck cancers. Here, we report the structural and functional basis by which the viral oncoprotein E7 hijacks host CRL2ZER1 to degrade retinoblastoma (Rb) protein and drive E2F-dependent proliferation. Crystal structures reveal that the N-terminal MH/N-degron of E7 engages a defined pocket within the armadillo (ARM)-repeat domain of ZER1. Disruption of this interface abolishes E7-ZER1 binding, prevents Rb degradation, silences E2F transcriptional programs, and impairs proliferation of HPV-positive cancer cells. Guided by these insights, we identify a first-in-class small-molecule inhibitor that blocks E7-ZER1 association, restores Rb stability, and selectively suppresses HPV-positive tumor growth in vivo. These results define a viral mimicry mechanism and nominate the ZER1 degron pocket as a ligandable therapeutic target for HPV-driven malignancies, highlighting translational opportunities for targeted therapy.
Introduction Despite advances in colorectal cancer (CRC) treatment, the chromosomal instability (CIN)-positive subgroup remains refractory to conventional therapies and immunotherapy. C2orf76, a poorly characterized gene identified as a CIN-linked candidate in CRC through bioinformatic analyses, has been associated with favorable prognosis and potential immune-related functions. However, its biological roles and underlying mechanisms in CRC remain largely unexplored. Methods To investigate the role of C2orf76, we generated knockout (KO), overexpression (OE), and rescue (RE) cell lines in CRC models. We performed RNA-seq, RT-qPCR, and Western blotting to examine transcriptomic and protein-level changes. Functional assays included proliferation, migration, cisplatin sensitivity, pyroptosis (GSDME cleavage), cytokinesis-block micronucleus assay (CBMN) for CIN, and γ-H2AX foci detection for DNA double-strand breaks. Results Unexpectedly, C2orf76 KO suppressed proliferation and migration, contradicting its favorable prognostic association and suggesting a complex regulatory role. RNA-seq revealed altered genes involved in chromosome segregation, cell cycle, platinum resistance, P53 signaling, and oncogenic pathways. RT-qPCR validated changes in chromosomal stability-related genes CDT1 and FOXM1, which were further verified by Western blotting. Further experiments showed that KO inhibited cisplatin-induced pyroptosis and cleavage of GSDME, whereas OE promoted migration and enhanced cisplatin sensitivity. The CBMN assay confirmed that C2orf76 significantly impacts chromosomal instability levels in CRC cells. C2orf76 KO cells also exhibited elevated γ-H2AX foci after cisplatin treatment. Rescue of C2orf76 expression reversed the KO-induced suppression of proliferation and migration, restored cisplatin sensitivity and pyroptosis, and reduced chromosomal instability. Discussion These findings unveil a context-dependent duality of C2orf76: knockout increases CIN, reduces proliferation and migration, but promotes chemoresistance; overexpression enhances cisplatin-induced pyroptosis and drug sensitivity yet increases migration. Thus, C2orf76 establishes a functional link between CIN, cell death, and therapeutic response, positioning it as a tunable target that may require context-dependent modulation for effective CRC intervention. This study not only characterizes a previously understudied gene but also provides a mechanistic framework for understanding how CIN-associated genes can exert opposing effects on tumor progression and treatment outcome.
Li Zhang, Zhu Song, Pin-Jie Zhang et al.· Frontiers in Oncology· 0 citations
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