Splice site m6A methylation prevents binding of DGCR8 to suppress KRT4 pre-mRNA splicing in oral squamous cell carcinoma

• DOI: 10.7717/peerj.14824
• Publication Date: 2023-02-16T09:56:28Z
• Authors: Xiaoxu Li; Juan Fang; Xiaoan Tao; Juan Xia; Bin Cheng; Yun Wang
• Keywords: 0303 health sciences; QH301-705.5; Squamous Cell Carcinoma of Head and Neck; R; RNA-Binding Proteins; Keratin 4; Biochemistry; Methylation; 3. Good health; MicroRNAs; 03 medical and health sciences; Pre-mRNA splicing; Oral squamous cell carcinoma; Head and Neck Neoplasms; Carcinoma, Squamous Cell; RNA Precursors; Medicine; Humans; Mouth Neoplasms; Keratin-4; m6A methylation; Biology (General)

Oral squamous cell carcinoma (OSCC) is the 11th most prevalent tumor worldwide. Despite advantages of therapeutic approaches, the 5-year survival rate of patients with OSCC is less than 50%. It is urgent to elucidate mechanisms underlying OSCC progression for developing novel treatment strategies. Our recent study has revealed that Keratin 4 (KRT4) suppresses OSCC development, which is downregulated in OSCC. Nevertheless, the mechanism downregulating KRT4 in OSCC remains unknown. In this study, touchdown PCR was utilized to detect KRT4 pre-mRNA splicing, while m6A RNA methylation was identified by methylated RNA immunoprecipitation (MeRIP). Besides, RNA immunoprecipitation (RIP) was used to determine RNA-protein interaction. Herein, this study indicated that intron splicing of KRT4 pre-mRNA was suppressed in OSCC. Mechanistically, m6A methylation of exon-intron boundaries prevented intron splicing of KRT4 pre-mRNA in OSCC. Besides, m6A methylation suppressed the binding of splice factor DGCR8 microprocessor complex subunit (DGCR8) to exon-intron boundaries in KRT4 pre-mRNA to prohibit intron splicing of KRT4 pre-mRNA in OSCC. These findings revealed the mechanism downregulating KRT4 in OSCC and provided potential therapeutic targets for OSCC.