Laboratory of Epigenetics, Institute of Biomedical Sciences, and Department of Biochemistry, Fudan University Medical School, Shanghai, China.
Mol Cell Biol. 2013 Mar;33(6):1139-48. doi: 10.1128/MCB.01191-12. Epub 2013 Jan 7.
UHRF1 (ubiquitin-like, with PHD and RING finger domains 1) is a critical epigenetic player involved in the maintenance of DNA methylation patterns during DNA replication. Dysregulation of the UHRF1 level is implicated in cancer onset, metastasis, and tumor recurrence. Previous studies demonstrated that UHRF1 can be stabilized through USP7-mediated deubiquitylation, but the mechanism through which UHRF1 is ubiquitylated is still unknown. Here we show that proteasomal degradation of UHRF1 is mediated by the SCF(β-TrCP) E3 ligase. Through bioinformatic and mutagenesis studies, we identified a functional DSG degron in the UHRF1 N terminus that is necessary for UHRF1 stability regulation. We further show that UHRF1 physically interacts with β-TrCP1 in a manner dependent on phosphorylation of serine 108 (S108(UHRF1)) within the DSG degron. Furthermore, we demonstrate that S108(UHRF1) phosphorylation is catalyzed by casein kinase 1 delta (CK1δ) and is important for the recognition of UHRF1 by SCF(β-TrCP). Importantly, we demonstrate that UHRF1 degradation is accelerated in response to DNA damage, coincident with enhanced S108(UHRF1) phosphorylation. Taken together, our data identify SCF(β-TrCP) as a bona fide UHRF1 E3 ligase important for regulating UHRF1 steady-state levels both under normal conditions and in response to DNA damage.
UHRF1（泛素样，具有 PH 和 RING 指结构域 1）是一种关键的表观遗传因子，参与 DNA 复制过程中 DNA 甲基化模式的维持。UHRF1 水平的失调与癌症的发生、转移和肿瘤复发有关。先前的研究表明，UHRF1 可以通过 USP7 介导的去泛素化而稳定，但是 UHRF1 被泛素化的机制尚不清楚。在这里，我们表明 UHRF1 的蛋白酶体降解是由 SCF（β-TrCP）E3 连接酶介导的。通过生物信息学和突变研究，我们在 UHRF1 N 端鉴定出一个功能 DSG 降解基序，该基序对于 UHRF1 稳定性调节是必需的。我们进一步表明，UHRF1 与 β-TrCP1 以依赖于 DSG 降解基序内丝氨酸 108（S108（UHRF1））磷酸化的方式相互作用。此外，我们证明 S108（UHRF1）磷酸化由酪蛋白激酶 1 德尔塔（CK1δ）催化，并且对于 SCF（β-TrCP）识别 UHRF1 很重要。重要的是，我们证明 UHRF1 降解在 DNA 损伤时加速，与 S108（UHRF1）磷酸化增强同时发生。总之，我们的数据确定 SCF（β-TrCP）为一种真正的 UHRF1 E3 连接酶，对于在正常条件下和响应 DNA 损伤时调节 UHRF1 的稳态水平都很重要。
