Department of Molecular Biology, Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, United States.
Department of Genetics, Harvard Medical School, Boston, United States.
Elife. 2019 Jan 24;8:e42341. doi: 10.7554/eLife.42341.
The zinc finger CCCTC-binding protein (CTCF) carries out many functions in the cell. Although previous studies sought to explain CTCF multivalency based on sequence composition of binding sites, few examined how CTCF post-translational modification (PTM) could contribute to function. Here, we performed CTCF mass spectrometry, identified a novel phosphorylation site at Serine 224 (Ser-P), and demonstrate that phosphorylation is carried out by Polo-like kinase 1 (PLK1). CTCF Ser-P is chromatin-associated, mapping to at least a subset of known CTCF sites. CTCF Ser-P accumulates during the G2/M transition of the cell cycle and is enriched at pericentric regions. The phospho-obviation mutant, S224A, appeared normal. However, the phospho-mimic mutant, S224E, is detrimental to mouse embryonic stem cell colonies. While ploidy and chromatin architecture appear unaffected, S224E mutants differentially express hundreds of genes, including p53 and p21. We have thus identified a new CTCF PTM and provided evidence of biological function.
锌指 CCCTC 结合蛋白（CTCF）在细胞中发挥多种功能。尽管先前的研究试图根据结合位点的序列组成来解释 CTCF 的多价性，但很少有研究检查 CTCF 翻译后修饰（PTM）如何有助于功能。在这里，我们进行了 CTCF 质谱分析，鉴定了丝氨酸 224 处的一个新磷酸化位点（Ser-P），并证明磷酸化是由 Polo 样激酶 1（PLK1）完成的。CTCF Ser-P 与染色质相关，至少映射到已知 CTCF 位点的一部分。CTCF Ser-P 在细胞周期的 G2/M 转换过程中积累，并在着丝粒区域富集。磷酸化缺失突变体 S224A 似乎正常。然而，磷酸化模拟突变体 S224E 对小鼠胚胎干细胞集落有害。虽然倍性和染色质结构似乎没有受到影响，但 S224E 突变体差异表达数百个基因，包括 p53 和 p21。因此，我们鉴定了一种新的 CTCF PTM，并提供了生物学功能的证据。
