LINC00673-V4 Promotes Colorectal Cancer Cell Proliferation by Interacting With FUS and Restoring the Expression of Hippo-YAP Target Genes.
TL;DR
This study investigated how LINC00673-V4 drives CRC proliferation by modulating the Hippo-Yes-associated protein (Hippo-YAP) signaling pathway and identified LINC00673-V4 as an isoform-specific oncogenic lncRNA in CRC.
Abstract
Background
Colorectal cancer (CRC) is a leading cause of cancer-related morbidity and mortality worldwide; thus, understanding its molecular mechanisms is critical for developing novel therapeutic targets. Long non-coding RNAs (lncRNAs) play crucial isoform-specific roles in cancer. While oncogenic lncRNA LINC00673 is known to be involved in multiple malignancies and possesses five distinct transcript variants, the functional role of LINC00673-V4-a highly expressed transcript variant in CRC-remains largely unexplored. This study investigated how LINC00673-V4 drives CRC proliferation by modulating the Hippo-Yes-associated protein (Hippo-YAP) signaling pathway.
Methods
Survival analysis was performed using the GSE39582 dataset to assess the prognostic value of LINC00673 in patients with CRC. The expression of LINC00673 transcript variants in CRC cell lines was detected by quantitative PCR. Cell Counting Kit-8 and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays were used to assess cell proliferation upon LINC00673-V4 knockdown or overexpression. Western blotting and immunofluorescence staining were utilized to analyze the expression of Hippo-YAP target genes. To confirm the interaction between LINC00673-V4 and fused in sarcoma (FUS), RNA immunoprecipitation (RIP) was performed, while co-IP was used to investigate potential protein-protein interactions.
Results
High LINC00673 expression was observed in CRC cell lines and was associated with a poor prognosis in patients with CRC. Among the five LINC00673 transcript variants, LINC00673-V3 and LINC00673-V4 were the predominantly expressed isoforms; however, only LINC00673-V4 significantly promoted CRC cell proliferation. LINC00673-V4 inhibited YAP phosphorylation at Ser127, promoted YAP nuclear translocation, and upregulated the expression of Hippo-YAP target genes (connective tissue growth factor, cysteine-rich angiogenic inducer 61, survivin). RIP assays confirmed an association between LINC00673-V4 and FUS, while co-immunoprecipitation (co-IP) assays revealed that FUS interacted with both YAP and large tumor suppressor 1 (LATS1), suggesting FUS may facilitate LATS1-mediated YAP phosphorylation. FUS was found to promote LATS1-mediated YAP Ser127 phosphorylation, induce YAP cytoplasmic retention, and down-regulate Hippo-YAP target gene expression. Rescue experiments showed that LINC00673-V4 reversed the FUS-induced suppression of Hippo-YAP target gene expression.
Conclusions
Our study identified LINC00673-V4 as an isoform-specific oncogenic lncRNA in CRC. By associating with FUS, LINC00673-V4 sequesters FUS away from the LATS1/YAP complex; thereby inhibiting FUS-mediated YAP phosphorylation and enhancing Hippo-YAP target gene expression. These findings expand the landscape of lncRNA isoform-specific regulation in cancer, highlighting LINC00673-V4 as a potential prognostic biomarker and therapeutic target for CRC.