CRYSTAL STRUCTURE OF THE KSHV PROCESSIVITY FACTOR, PF-8

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 人类疱疹病毒8型(HHV-8)又称卡波西肉瘤相关人类疱疹病毒(KSHV)，是一种伽玛疱疹病毒，可引起卡波西肉瘤、原发渗出性淋巴瘤和多中心Castleman病等淋巴增生性疾病。KSHV编码病毒处理因子PF-8，它与DNA结合，在DNA合成过程中保持病毒聚合酶Pol-8和DNA之间的接触是必不可少的。甲型疱疹病毒HSV-1和乙型疱疹病毒HCMV的过程性因子的晶体结构与真核细胞过程性因子增殖细胞核抗原的结构相似，但它们的四级重排除外。增殖细胞核抗原在DNA周围形成一个三聚体环，而HSV-1和HCMV的加工性因子分别是单体和二聚体，不需要钳制加载器或ATP就可以加载到DNA上。我们测定了PF-8到2.8°的晶体结构，并表明PF-8形成一种头对头的同源二聚体，在功能上似乎落在UL42和UL44的结构之间的某个地方。基于结构数据，我们能够确定可能与DNA和聚合酶相互作用的部位，提出一个同时作用于复合体的所有三个组分的模型。此外，所有三类疱疹病毒的晶体结构的可用性为比较结构和功能提供了新的见解。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Human herpesvirus-8 (HHV-8), also known as Karposi's sarcoma-associated human herpesvirus (KSHV), is a gammaherpesvirus that is the causative agent of various lymphoproliferative disorders including Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. KSHV encodes the viral processivity factor, PF-8, which binds to DNA and is essential for maintaining contact between the viral polymerase Pol-8 and DNA during DNA synthesis. The crystal structures of a processivity factor from the alpha herpesvirus, HSV-1, and the beta herpesvirus, HCMV, revealed structures similar to that of the eukaryotic processivity factor, proliferating cell nuclear antigen (PCNA), except in their quaternary rearrangement. PCNA forms a trimeric ring around DNA while the processivity factors from HSV-1 and HCMV are a monomer and dimer respectively and do not require a clamp loader or ATP in order to be loaded onto DNA. We have determined the crystal structure of PF-8 to 2.8¿, and show that PF-8 forms a head-to-head homodimer that appears to fall, functionally, somewhere between the structures of UL42 and UL44. Based on the structural data, we are able to identify possible sites for interactions with DNA and polymerase, to propose a model for the simultaneous interaction of all three components of the complex. In addition, the availability of crystal structures for all three herpesvirus classes provides new insights into comparative structure and function.