The Wistar Institute, Philadelphia, PA, USA.
The Wistar Institute, Philadelphia, PA, USA.
Cell. 2021 Feb 4;184(3):643-654.e13. doi: 10.1016/j.cell.2020.12.022. Epub 2021 Jan 21.
Epstein-Barr virus (EBV) is an oncogenic human herpesvirus that persists as a multicopy episome in proliferating host cells. Episome maintenance is strictly dependent on EBNA1, a sequence-specific DNA-binding protein with no known enzymatic activities. Here, we show that EBNA1 forms a cell cycle-dependent DNA crosslink with the EBV origin of plasmid replication oriP. EBNA1 tyrosine 518 (Y518) is essential for crosslinking to oriP and functionally required for episome maintenance and generation of EBV-transformed lymphoblastoid cell lines (LCLs). Mechanistically, Y518 is required for replication fork termination at oriP in vivo and for formation of SDS-resistant complexes in vitro. EBNA1-DNA crosslinking corresponds to single-strand endonuclease activity specific to DNA structures enriched at replication-termination sites, such as 4-way junctions. These findings reveal that EBNA1 forms tyrosine-dependent DNA-protein crosslinks and single-strand cleavage at oriP required for replication termination and viral episome maintenance.
EB 病毒（EBV）是一种致癌性人类疱疹病毒，以多拷贝的附加体形式存在于增殖的宿主细胞中。附加体的维持严格依赖于 EBNA1，这是一种具有序列特异性的 DNA 结合蛋白，没有已知的酶活性。在这里，我们发现 EBNA1 与 EBV 质粒复制原点 oriP 形成细胞周期依赖性 DNA 交联。EBNA1 酪氨酸 518（Y518）对于 oriP 的交联以及对于附加体的维持和 EBV 转化的淋巴母细胞系（LCL）的产生都是必需的。从机制上讲，Y518 在体内 oriP 处复制叉终止以及体外形成 SDS 抗性复合物是必需的。EBNA1-DNA 交联对应于单链内切酶活性，该活性特异性针对富含复制终止位点的 DNA 结构，如 4 向连接。这些发现表明，EBNA1 在 oriP 处形成依赖于酪氨酸的 DNA-蛋白质交联和单链切割，这是复制终止和病毒附加体维持所必需的。
