Department of Gastroenterology, Jinshan Hospital, Fudan University, 1508 Longhang Road, Shanghai, 201508, China.
Department of Anaesthesiology, Shanghai Public Health Clinical Center, Fudan University, 2901 Caolang Road, Shanghai, 201503, China.
Cell Death Dis. 2022 Feb 2;13(2):98. doi: 10.1038/s41419-022-04509-1.
Long non-coding RNAs (lncRNAs) play critical functions in various cancers. Firre intergenic repeating RNA element (FIRRE), a lncRNA located in the nucleus, was overexpressed in colorectal cancer (CRC). However, the detailed mechanism of FIRRE in CRC remains elusive. Results of RNA sequence and qPCR illustrated overexpression of FIRRE in CRC cell lines and tissues. The aberrant expression of FIRRE was correlated with the migration, invasion, and proliferation in cell lines. In accordance, it was also associated with lymphatic metastasis and distant metastasis in patients with CRC. FIRRE was identified to physically interact with Polypyrimidine tract-binding protein (PTBP1) by RNA pull-down and RNA immunoprecipitation (RIP). Overexpression of FIRRE induced the translocation of PTBP1 from nucleus to cytoplasm, which was displayed by immunofluorescence and western blot. In turn, delocalization of FIRRE from nucleus to cytoplasm is observed after the loss of PTBP1. The RNA-protein complex in the cytoplasm directly bound to BECN1 mRNA, and the binding site was at the 3' end of the mRNA. Cells with FIRRE and PTBP1 depletion alone or in combination were treated by Actinomycin D (ACD). Results of qPCR showed FIRRE stabilized BECN1 mRNA in a PTBP1-medieated manner. In addition, FIRRE contributed to autophagy activity. These findings indicate FIRRE acts as an oncogenic factor in CRC, which induces tumor development through stabilizing BECN1 mRNA and facilitating autophagy in a PTBP1-mediated manner.
长链非编码 RNA（lncRNA）在各种癌症中发挥着关键作用。FIRRE（intergenic repeating RNA element）是一种位于细胞核内的 lncRNA，在结直肠癌（CRC）中过表达。然而，FIRRE 在 CRC 中的详细机制仍不清楚。RNA 序列和 qPCR 的结果表明，FIRRE 在 CRC 细胞系和组织中过表达。FIRRE 的异常表达与细胞系中的迁移、侵袭和增殖相关。相应地，它也与 CRC 患者的淋巴转移和远处转移相关。RNA 下拉和 RNA 免疫沉淀（RIP）实验表明，FIRRE 与多嘧啶 tract 结合蛋白（PTBP1）发生物理相互作用。过表达 FIRRE 诱导 PTBP1 从细胞核易位到细胞质，免疫荧光和 Western blot 显示了这一点。相反，在失去 PTBP1 后，FIRRE 从细胞核到细胞质的定位被观察到。细胞质中的 RNA-蛋白复合物直接与 BECN1 mRNA 结合，结合位点位于 mRNA 的 3' 端。单独或联合敲除 FIRRE 和 PTBP1 的细胞用放线菌素 D（ACD）处理。qPCR 的结果表明，FIRRE 以 PTBP1 介导的方式稳定 BECN1 mRNA。此外，FIRRE 促进自噬活性。这些发现表明，FIRRE 在 CRC 中作为致癌因子发挥作用，通过稳定 BECN1 mRNA 并以 PTBP1 介导的方式促进自噬来诱导肿瘤发展。
