SUMO化修饰是一种把小泛素相关修饰物(small ubiquition related modifier,SUMO)共价连接到细胞内靶蛋白半胱氨酸残基上的一种蛋白质翻译后修饰。SUMO化修饰参与并调控着多种细胞进程,如转录调控、核转运和信号转导等。SUMO化修饰是一种动态可逆的修饰方式。SUMO特异性蛋白酶(SUMO-specific proteases,SENPs)可以使SUMO化修饰的蛋白质发生去SUMO化,在维持细胞内SUMO化与去SUMO化的平衡中起重要作用。研究表明,SENPs与多种癌症的发生发展密切相关,如SENP1能直接调节多条致癌通路,诱发正常的前列腺上皮细胞状态异常。癌细胞中的SENP3能诱导血管生成。因此,对去SUMO化机制研究可以为开发癌症治疗药物提供新的思路。
Objective:Kaiso is upregulated in many cancers and proposed to bind with both methylated- and unmethylated-DNA in the nucleus as a transcriptional repressor.The objective is to define its subcellular localization in vivo and exact binding DNA sequences in cells.Methods:Compartmentalization of exogenous Kaiso in cells was tracked with enhanced green fluorescence protein(EGFP) tag.The endogenous Kaiso expression in gastric carcinoma tissue was examined with immunohistochemical staining.Kaiso-DNA binding was tested using electrophoretic mobility shift assay(EMSA) and chromatin immunoprecipitation assay(ChIP).Results:Kaiso mainly localized in the nucleus of cancer and stromal cells in vivo,but remained in the cytoplasm of cultured cells.Most importantly,nuclear Kaiso can bind with the methylated-CGCGcontaining sequence in the CDKN2 A promoter,but not with the hydroxymethylated-CGCG sequence in HCT116 cells.Conclusions:Kaiso locates mainly in the nucleus in vivo where it binds with the methylated-CGCG sequences,but does not bind with the hydroxymethylated-CGCG sequences.
Sisi QinBaozhen ZhangWei TianLiankun GuZheming LuDajun Deng
