Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Republic of Korea.
Department of Bioscience, University of Science and Technology KRIBB School, Daejeon, Republic of Korea.
PLoS Biol. 2019 Jul 19;17(7):e3000367. doi: 10.1371/journal.pbio.3000367. eCollection 2019 Jul.
Human papillomaviruses (HPVs) are causative agents of various diseases associated with cellular hyperproliferation, including cervical cancer, one of the most prevalent tumors in women. E7 is one of the two HPV-encoded oncoproteins and directs recruitment and subsequent degradation of tumor-suppressive proteins such as retinoblastoma protein (pRb) via its LxCxE motif. E7 also triggers tumorigenesis in a pRb-independent pathway through its C-terminal domain, which has yet been largely undetermined, with a lack of structural information in a complex form with a host protein. Herein, we present the crystal structure of the E7 C-terminal domain of HPV18 belonging to the high-risk HPV genotypes bound to the catalytic domain of human nonreceptor-type protein tyrosine phosphatase 14 (PTPN14). They interact directly and potently with each other, with a dissociation constant of 18.2 nM. Ensuing structural analysis revealed the molecular basis of the PTPN14-binding specificity of E7 over other protein tyrosine phosphatases and also led to the identification of PTPN21 as a direct interacting partner of E7. Disruption of HPV18 E7 binding to PTPN14 by structure-based mutagenesis impaired E7's ability to promote keratinocyte proliferation and migration. Likewise, E7 binding-defective PTPN14 was resistant for degradation via proteasome, and it was much more effective than wild-type PTPN14 in attenuating the activity of downstream effectors of Hippo signaling and negatively regulating cell proliferation, migration, and invasion when examined in HPV18-positive HeLa cells. These results therefore demonstrated the significance and therapeutic potential of the intermolecular interaction between HPV E7 and host PTPN14 in HPV-mediated cell transformation and tumorigenesis.
人乳头瘤病毒（HPV）是导致各种与细胞过度增殖相关疾病的病原体，包括宫颈癌，宫颈癌是女性中最常见的肿瘤之一。E7 是 HPV 编码的两种致癌蛋白之一，通过其 LxCxE 基序指导募集和随后降解肿瘤抑制蛋白，如视网膜母细胞瘤蛋白（pRb）。E7 还通过其 C 末端结构域在 pRb 非依赖性途径中引发肿瘤发生，但其结构域的大部分功能尚未确定，与宿主蛋白形成复合物时缺乏结构信息。在此，我们展示了 HPV18 的 E7 C 末端结构域与人类非受体型蛋白酪氨酸磷酸酶 14（PTPN14）的催化结构域结合的晶体结构，该结构域属于高危 HPV 基因型。它们直接且强效地相互作用，解离常数为 18.2 nM。随后的结构分析揭示了 E7 与其他蛋白酪氨酸磷酸酶结合的特异性的分子基础，也导致了鉴定出 PTPN21 是 E7 的直接相互作用伙伴。基于结构的诱变破坏 HPV18 E7 与 PTPN14 的结合，损害了 E7 促进角质形成细胞增殖和迁移的能力。同样，E7 结合缺陷型 PTPN14 不易通过蛋白酶体降解，并且当其在 HPV18 阳性 HeLa 细胞中研究时，比野生型 PTPN14 更有效地抑制 Hippo 信号下游效应物的活性并负调控细胞增殖、迁移和侵袭。因此，这些结果证明了 HPV E7 与宿主 PTPN14 之间的分子间相互作用在 HPV 介导的细胞转化和肿瘤发生中的重要性和治疗潜力。
