National Engineering Laboratory for AIDS Vaccine, College of Life Science, Jilin University, Changchun, Jilin Province, 130012, People's Republic of China.
Genes Chromosomes Cancer. 2013 Jul;52(7):644-55. doi: 10.1002/gcc.22060. Epub 2013 Apr 30.
In hepatocellular carcinomas (HCCs), the levels of histone H3 dimethylation at lysine 9 (H3K9me2) and its corresponding histone methyltransferase G9a are significantly elevated. Recently, G9a was reported to form a complex with the H3K9 methylation effector protein CDYL, but little is known about the expression of CDYL in HCC patients. The human CDYL gene produces two transcripts, a long form (CDYLa) and a short form (CDYLb), but it is unclear whether the protein products have different functions. The aim of this study was to investigate the distinctions between CDYLa and CDYLb and their expression levels in HCC tissues. We first examined binding abilities of the different CDYL forms with methylated H3 peptides by a pull-down assay. Human CDYLb (h-CDYLb) specifically recognized H3Kc9me2 and H3Kc9me3 modifications, whereas human CDYLa (h-CDYLa) did not interact with any methylated H3 peptides. Similarly, mouse CDYLb (m-CDYLb) specifically bound with di- and tri-methylated H3Kc9 peptides, while mouse CDYLa (m-CDYLa) lacked that ability. Affinity purification also was used to identify the distinct composition of the h-CDYLa or h-CDYLb protein complex. h-CDYLb was found in a multiprotein complex with G9a and GLP, while the h-CDYLa complex did not contain these two enzymes. Consistent with the protein complex composition, h-CDYLb and G9a were both upregulated in HCC tissues, compared with adjacent non-cancerous liver tissues. Furthermore, the positive correlation between expression levels of h-CDYLb and G9a was statistically significant. In contrast, h-CDYLa showed no enrichment in HCC tissues. These findings suggest that h-CDYLb and G9a are cooperatively involved in HCC.
在肝细胞癌（HCCs）中，组蛋白 H3 赖氨酸 9 二甲基化（H3K9me2）及其相应的组蛋白甲基转移酶 G9a 的水平显著升高。最近，有报道称 G9a 与 H3K9 甲基化效应蛋白 CDYL 形成复合物，但关于 HCC 患者中 CDYL 的表达情况知之甚少。人类 CDYL 基因产生两种转录本，一种是长型（CDYLa），另一种是短型（CDYLb），但不清楚其蛋白产物是否具有不同的功能。本研究旨在探讨 CDYLa 和 CDYLb 之间的区别及其在 HCC 组织中的表达水平。我们首先通过下拉实验检测了不同 CDYL 形式与甲基化 H3 肽的结合能力。人 CDYLb（h-CDYLb）特异性识别 H3Kc9me2 和 H3Kc9me3 修饰，而人 CDYLa（h-CDYLa）与任何甲基化 H3 肽均无相互作用。同样，鼠 CDYLb（m-CDYLb）特异性结合二甲基化和三甲基化 H3Kc9 肽，而鼠 CDYLa（m-CDYLa）则缺乏这种能力。亲和纯化也用于鉴定 h-CDYLa 或 h-CDYLb 蛋白复合物的不同组成。h-CDYLb 存在于与 G9a 和 GLP 组成的多蛋白复合物中，而 h-CDYLa 复合物中不含有这两种酶。与蛋白复合物组成一致，h-CDYLb 和 G9a 在 HCC 组织中均上调，与相邻的非癌性肝组织相比。此外，h-CDYLb 和 G9a 的表达水平之间存在显著的正相关。相比之下，h-CDYLa 在 HCC 组织中没有富集。这些发现表明 h-CDYLb 和 G9a 协同参与了 HCC。
