Department of Clinical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Autophagy Research Center, Department of Clinical Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Zand Street, Shiraz, 71348-14336, Iran.
Med Oncol. 2023 Jun 9;40(7):199. doi: 10.1007/s12032-023-02039-0.
Colorectal cancer (CRC) is a prevalent gastrointestinal neoplasm that ranks fourth in terms of cancer-related deaths worldwide. In the process of CRC progression, multiple ubiquitin-conjugating enzymes (E2s) are involved; UBE2Q1 is one of those newly identified E2s that is markedly expressed in human colorectal tumors. Since p53 is a well-known tumor suppressor and defined as a key factor to be targeted by the ubiquitin-proteasome system, we hypothesized that UBE2Q1 might contribute to CRC progression through the modulation of p53. Using the lipofection method, the cultured SW480 and LS180 cells were transfected with the UBE2Q1 ORF-containing pCMV6-AN-GFP vector. Then, quantitative RT-PCR was used to assay the mRNA expression levels of p53's target genes, i.e., Mdm2, Bcl2, and Cyclin E. Moreover, Western blot analysis was performed to confirm the cellular overexpression of UBE2Q1 and assess the protein levels of p53, pre- and post-transfection. The expression of p53's target genes were cell line-dependent except for Mdm2 that was consistent with the findings of p53. The results of Western blotting demonstrated that the protein levels of p53 were greatly lower in UBE2Q1-transfected SW480 cells compared to the control SW480 cells. However, the reduced levels of p53 protein were not remarkable in the transfected LS180 cells compared to the control cells. The suppression of p53 is believed to be the result of UBE2Q1-dependent ubiquitination and its subsequent proteasomal degradation. Furthermore, the ubiquitination of p53 can act as a signal for degradation-independent functions, such as nuclear export and suppressing the p53's transcriptional activities. In this context, the decreased Mdm2 levels can moderate the proteasome-independent mono-ubiquitination of p53. The ubiquitinated p53 modulates the transcriptional levels of target genes. Therefore, the up-modulation of UBE2Q1 may influence the transcriptional activities depending on p53, and thereby contributes to CRC progression through regulating the p53.
结直肠癌（CRC）是一种常见的胃肠道肿瘤，在全球癌症相关死亡中排名第四。在 CRC 进展过程中，涉及多种泛素连接酶（E2s）；UBE2Q1 是新鉴定的 E2s 之一，在人类结直肠肿瘤中明显表达。由于 p53 是一种众所周知的肿瘤抑制因子，并被定义为泛素-蛋白酶体系统的关键靶向因子，我们假设 UBE2Q1 可能通过调节 p53 促进 CRC 的进展。使用脂质体转染法，用含有 UBE2Q1 ORF 的 pCMV6-AN-GFP 载体转染培养的 SW480 和 LS180 细胞。然后，使用定量 RT-PCR 检测 p53 靶基因 Mdm2、Bcl2 和 Cyclin E 的 mRNA 表达水平。此外，进行 Western blot 分析以确认 UBE2Q1 的细胞过表达，并评估转染前后 p53 的蛋白水平。除了 Mdm2 与 p53 的发现一致外，p53 靶基因的表达与细胞系有关。Western blot 结果表明，与对照 SW480 细胞相比，UBE2Q1 转染的 SW480 细胞中 p53 蛋白水平显着降低。然而，与对照细胞相比，转染的 LS180 细胞中 p53 蛋白水平的降低并不明显。p53 的抑制被认为是 UBE2Q1 依赖性泛素化及其随后的蛋白酶体降解的结果。此外，p53 的泛素化可以作为降解非依赖性功能的信号，例如核输出和抑制 p53 的转录活性。在这种情况下，Mdm2 水平的降低可以调节 p53 的非蛋白酶体单泛素化。泛素化的 p53 调节靶基因的转录水平。因此，UBE2Q1 的上调可能会影响依赖 p53 的转录活性，从而通过调节 p53 促进 CRC 的进展。
