Sun Zhiguo, Xiao Bingyi, Jha Hem Chandra, Lu Jie, Banerjee Shuvomoy, Robertson Erle S
Department of Microbiology and Tumor Virology Program, Abramson Comprehensive Cancer Center, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Department of Microbiology and Tumor Virology Program, Abramson Comprehensive Cancer Center, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
J Virol. 2014 Jul;88(13):7367-78. doi: 10.1128/JVI.00554-14. Epub 2014 Apr 16.
Kaposi's sarcoma-associated herpesvirus (KSHV) has a significant contributory role in the development of three major human neoplastic or lymphoproliferative diseases: Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). These diseases are associated with chromosomal instability, a hallmark of human cancer. The latency-associated nuclear antigen (LANA) encoded by KSHV plays a key role in regulating a number of cellular pathways critical for oncogenesis. KSHV LANA alone can induce the development of B-cell hyperplasia and lymphoma in mice expressing LANA. LANA also induces chromosomal instability, thus promoting oncogenesis. However, the precise mechanism underlying LANA-mediated chromosomal instability remains uncharted. Here we report that LANA promoted the induction of chromosomal instability and the formation of micronuclei and multinucleation through its interaction with one of the critical spindle checkpoint proteins, Bub1, and the resulting degradation of Bub1. This interaction occurs through the Knl and kinase domains of Bub1, identified as important for stability and degradation. These results suggest that LANA can dysregulate Bub1 activity, which leads to aberrant chromosome replication and aneuploidy, thus contributing to KSHV-mediated oncogenesis.
This work represents the first set of results identifying a novel mechanism by which LANA, a latency-associated antigen encoded by KSHV, can induce the degradation of Bub1, a spindle checkpoint protein that is important for spindle checkpoint signaling and chromosome segregation. The downregulation of Bub1 mediated by LANA resulted in chromosomal instability, a hallmark of cancer. We further investigated the specific domains of Bub1 that are required for the interaction between LANA and Bub1. The results demonstrated that the Knl and kinase domains of Bub1 are required for the interaction between LANA and Bub1. In addition, we also investigated the mechanism by which LANA promoted Bub1 degradation. Our results showed that LANA interacted physically with the anaphase-promoting complex (APC/C), thus promoting the degradation of Bub1 in a ubiquitin-dependent process.
卡波西肉瘤相关疱疹病毒（KSHV）在三种主要的人类肿瘤性或淋巴增殖性疾病的发生发展中起重要作用：卡波西肉瘤（KS）、原发性渗出性淋巴瘤（PEL）和多中心性Castleman病（MCD）。这些疾病与染色体不稳定性相关，而染色体不稳定性是人类癌症的一个标志。KSHV编码的潜伏相关核抗原（LANA）在调节许多对肿瘤发生至关重要的细胞途径中起关键作用。单独的KSHV LANA可在表达LANA的小鼠中诱导B细胞增生和淋巴瘤的发生。LANA还可诱导染色体不稳定性，从而促进肿瘤发生。然而，LANA介导染色体不稳定性的精确机制仍不清楚。在此我们报告，LANA通过与关键的纺锤体检查点蛋白之一Bub1相互作用并导致Bub1降解，促进了染色体不稳定性的诱导以及微核和多核的形成。这种相互作用通过Bub1的Knl和激酶结构域发生，这两个结构域对稳定性和降解很重要。这些结果表明，LANA可失调Bub1活性，导致异常的染色体复制和非整倍体，从而促进KSHV介导的肿瘤发生。
这项工作代表了第一组结果，确定了一种新机制，即KSHV编码的潜伏相关抗原LANA可诱导Bub1降解，Bub1是一种对纺锤体检查点信号传导和染色体分离很重要的纺锤体检查点蛋白。LANA介导的Bub1下调导致染色体不稳定性，这是癌症的一个标志。我们进一步研究了LANA与Bub1相互作用所需的Bub1的特定结构域。结果表明，Bub1的Knl和激酶结构域是LANA与Bub1相互作用所必需的。此外，我们还研究了LANA促进Bub1降解的机制。我们的结果表明，LANA与后期促进复合物（APC/C）发生物理相互作用，从而在泛素依赖性过程中促进Bub1的降解。
