Maintenance of Human Papillomavirus Genomes

描述（由申请人提供）：高风险的肛门生殖器乳头瘤病毒（hpv）与全世界95%的浸润性宫颈癌有关。这些病毒在层状鳞状上皮中感染和复制，在那里它们可以持续很长时间。双链环状HPV基因组DNA在有丝分裂活性的基底层角质形成细胞中作为低拷贝数的核质粒维持。反式作用病毒因子E1和E2在复制过程中起重要作用；El，一种解旋酶，将Polalpha招募到原点；E2通过其结合位点结合E1和病毒基因组协同作用。对牛乳头瘤病毒1型（BPV-1）的研究表明，E2介导新合成的病毒基因组通过与有丝分裂染色体连接而分离到子细胞。我们最近开发了一个基于酵母的系统来研究HPV16复制和维持的顺式和反式需求。在该系统和人类细胞中进行的实验表明，E2对于HPV16基因组的长期维持可能并不严格要求。这一结果提示，HPV16染色体外维持的顺式和反式需要进一步评估。本提案的目标是：(1)研究E2在HPV16维持中的作用；(2)绘制HPV16基因组中独立于E2提供维持功能的顺式作用元件；(3)确定有助于基因组维持的细胞因子。这些研究将阐明这些致癌病毒在宿主体内维持其基因组的机制。

DESCRIPTION (provided by applicant): High-risk anogenital papillomaviruses (HPVs) are associated with 95% of invasive cervical cancers worldwide. These viruses infect and replicate in stratified squamous epithelia, where they can persist for long periods. The double-stranded circular HPV genomic DNA is maintained as a low-copy-number nuclear plasmid in the mitotically active basal layer keratinocytes. Trans-acting viral factors E1 and E2 play an important role in replication; El, a helicase, recruits Polalpha to the origin; E2 acts cooperatively by binding E1 and the viral genome through its binding sites. Studies of bovine papillomavirus type 1 (BPV-1) suggest that E2 mediates segregation of newly synthesized viral genomes to daughter cells by linking them to mitotic chromosomes. We have recently developed a yeast-based system to study the cis and trans requirements for HPV16 replication and maintenance. Experiments performed in this system and in human cells indicate that E2 may not be strictly required for long-term maintenance of HPV16 genomes. This result suggests that the cis and trans requirements for extrachromosomal maintenance of HPV16 need to be further evaluated. The objectives of this proposal are: (1) To investigate the role of E2 in HPV16 maintenance; (2) To map cis-acting elements in the HPV16 genome that provide maintenance functions independently of E2; and (3) To identify cellular factors that contribute to genome maintenance. These studies will clarify the mechanism by which these oncogenic viruses maintain their genomes in the host.