Drug Discovery, Otsuka Pharma, 9900 Medical Centre Drive, Rockville, MD 20850, USA.
Cell Biol Toxicol. 2012 Dec;28(6):409-19. doi: 10.1007/s10565-012-9232-z. Epub 2012 Sep 15.
TCPTP is an ubiquitously expressed tyrosine phosphatase with a predominant nuclear isoform (TC45) that binds DNA and has a role in G1-S cell cycle progression. Its deregulation by overexpression induces p53-dependent apoptosis, but the physiological role of its DNA-binding function is not known. Using immunocytochemistry and subcellular fractionation, we investigated changes in its localization in response to DNA damage and replication arrest. Rat fibroblasts showed an increase in endogenous TCPTP bound to nuclear components 3 h after exposure to sublethal dose of UV irradiation. Fractionation of nuclei showed an increase in chromatin and nuclear matrix associated component of TC45. After UV treatment, cells showed a concentration of TCPTP in discrete foci and enhanced colocalization with PCNA and p53BP1. Cells arrested at G1-S transition by hydroxyurea showed a loss of the predominant nuclear staining of TCPTP and an increase in cytoplasmic staining. Upon release from replication block, there was a time-dependent increase in number of cells showing prominent nuclear localization. This change in localization coincides with that of PCNA and Cdk2, two other nuclear proteins having functions in DNA replication. These results provide evidence for the regulation of TCPTP in response to DNA damage and replication stress. Dynamic changes in its localization coincident with that of PCNA suggest involvement of TCPTP in DNA repair and replication.
TCPTP 是一种广泛表达的酪氨酸磷酸酶，其主要核型（TC45）与 DNA 结合，并在 G1-S 细胞周期进展中发挥作用。其通过过表达而失调会诱导依赖 p53 的细胞凋亡，但它的 DNA 结合功能的生理作用尚不清楚。我们使用免疫细胞化学和亚细胞分级分离技术，研究了其在应对 DNA 损伤和复制停滞时定位的变化。暴露于亚致死剂量的紫外线照射 3 小时后，大鼠成纤维细胞中内源 TCPTP 与核成分的结合增加。核的分级分离显示染色质和核基质相关成分 TC45 的增加。UV 处理后，细胞中 TCPTP 集中在离散焦点中，并与 PCNA 和 p53BP1 增强共定位。通过羟基脲阻滞在 G1-S 转换期的细胞显示出 TCPTP 的主要核染色丢失和细胞质染色增加。从复制阻断中释放后，显示出明显核定位的细胞数量呈时间依赖性增加。这种定位的变化与 PCNA 和 Cdk2 的变化一致，PCNA 和 Cdk2 是另外两种具有 DNA 复制功能的核蛋白。这些结果为 TCPTP 响应 DNA 损伤和复制应激的调节提供了证据。其定位与 PCNA 的变化一致，表明 TCPTP 参与 DNA 修复和复制。
