KH domain-containing RNA-binding protein QKI (isoform 6) (QKI-6)

Quaking gene isoform 6 (QKI-6) is a critical splice variant of the KH domain-containing RNA-binding protein QKI, a member of the STAR (Signal Transduction and Activation of RNA) protein family [2, 16]. Primarily localized in both the cytoplasm and nucleus, QKI-6 regulates the post-transcriptional fate of target mRNAs by binding to Quaking Response Elements (QREs), thereby modulating alternative splicing, mRNA stability, and translation [2, 13, 16, 20]. It plays a fundamental role in the central and peripheral nervous systems by driving the differentiation of myelin-forming cells, such as oligodendrocytes and Schwann cells, and its dysregulation is linked to neuropsychiatric disorders like schizophrenia [2, 3, 16, 18, 22]. In oncology, QKI-6 exhibits a dual role: it serves as a tumor suppressor in non-small cell lung cancer and bladder cancer by inhibiting epithelial-mesenchymal transition (EMT) and cell proliferation, while conversely acting as an oncogenic factor in glioblastoma stem cells [1, 9, 10, 11, 23]. Currently, no small-molecule inhibitors are approved for clinical use, but therapeutic strategies focus on RNA-based modalities, including microRNA mimics (e.g., miR-29a agomirs) and gene therapy vectors, to restore or inhibit its function depending on the disease context [9, 11, 18]. Clinical development is challenged by the protein's essential role in myelination, which necessitates precise targeting to avoid systemic neurological toxicity [18, 20].

Other names

QKI6HQKI-6Quaking gene isoform 6 proteinProtein quaking isoform 6KH domain-containing RNA-binding protein QKI isoform 6

Pharmacological intervention focuses on modulating QKI-6 expression levels to either restore its tumor-suppressive functions (via gene therapy or mRNA stabilization) or inhibit its oncogenic activity (via microRNA-mediated silencing or RNA interference) [1, 9, 11, 18]. Endogenous QKI-6 binds to Quaking Response Elements (QREs) to regulate the splicing, stability, and translation of downstream targets critical for cell cycle control and myelination [2, 13, 20].