Key Laboratory of Drug Target and Drug for Degenerative Disease, School of Medicine & Holistic Integrative Medicine, Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China.
National Center for Colorectal Diseases, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, Jiangsu, China.
J Biol Chem. 2023 Feb;299(2):102876. doi: 10.1016/j.jbc.2023.102876. Epub 2023 Jan 6.
Aberrant expression of serine/arginine-rich splicing factor 2 (SRSF2) can lead to tumorigenesis, but its molecular mechanism in colorectal cancer is currently unknown. Herein, we found SRSF2 to be highly expressed in human colorectal cancer (CRC) samples compared with normal tissues. Both in vitro and in vivo, SRSF2 significantly accelerated the proliferation of colon cancer cells. Using RNA-seq, we screened and identified 33 alternative splicing events regulated by SRSF2. Knockdown of SLMAP-L or CETN3-S splice isoform could suppress the growth of colon cancer cells, predicting their role in malignant proliferation of colon cancer cells. Mechanistically, the in vivo crosslinking immunoprecipitation assay demonstrated the direct binding of the RNA recognition motif of SRSF2 protein to SLMAP and CETN3 pre-mRNAs. SRSF2 activated the inclusion of SLMAP alternative exon 24 by binding to constitutive exon 25, while SRSF2 facilitated the exclusion of CETN3 alternative exon 5 by binding to neighboring exon 6. Knockdown of SRSF2, its splicing targets SLMAP-L, or CETN3-S caused colon cancer cells to arrest in G1 phase of the cell cycle. Rescue of SLMAP-L or CETN3-S splice isoform in SRSF2 knockdown colon cancer cells could effectively reverse the inhibition of cell proliferation by SRSF2 knockdown through mediating cell cycle progression. Importantly, the percentage of SLMAP exon 24 inclusion increased and CETN3 exon 5 inclusion decreased in CRC samples compared to paired normal samples. Collectively, our findings identify that SRSF2 dysregulates colorectal carcinoma proliferation at the molecular level of splicing regulation and reveal potential splicing targets in CRC patients.
丝氨酸/精氨酸丰富剪接因子 2（SRSF2）的异常表达可导致肿瘤发生，但它在结直肠癌中的分子机制目前尚不清楚。在此，我们发现 SRSF2 在人结直肠癌（CRC）样本中的表达明显高于正常组织。无论是在体外还是体内，SRSF2 都能显著加速结肠癌细胞的增殖。通过 RNA-seq，我们筛选并鉴定了 33 种受 SRSF2 调控的剪接事件。SLMAP-L 或 CETN3-S 剪接异构体的敲低可抑制结肠癌细胞的生长，预示着它们在结肠癌细胞的恶性增殖中发挥作用。在机制上，体内交联免疫沉淀试验表明 SRSF2 蛋白的 RNA 识别基序可直接与 SLMAP 和 CETN3 前体 mRNA 结合。SRSF2 通过与组成性外显子 25 结合，激活 SLMAP 替代外显子 24 的包含，而 SRSF2 通过与邻近的外显子 6 结合，促进 CETN3 替代外显子 5 的排除。SRSF2、其剪接靶标 SLMAP-L 或 CETN3-S 的敲低可导致结肠癌细胞在细胞周期的 G1 期停滞。SRSF2 敲低结肠癌细胞中 SLMAP-L 或 CETN3-S 剪接异构体的恢复可通过调节细胞周期进程有效地逆转 SRSF2 敲低对细胞增殖的抑制作用。重要的是，与配对的正常样本相比，CRC 样本中的 SLMAP 外显子 24 包含增加，CETN3 外显子 5 包含减少。总之，我们的研究结果表明，SRSF2 通过调控剪接在分子水平上失调结直肠癌细胞的增殖，并揭示了结直肠癌患者潜在的剪接靶标。
