Kaposi sarcoma herpesvirus lytic replication is independent of the anaphase promoting complex activity.

Abstract

The anaphase promoting complex or cyclosome (APC/C) is a large E3 ubiquitin ligase, composed of 14 subunits. The activity of APC/C oscillates during the cell cycle to ensure a timely transition through each phase by promoting the degradation of important cell cycle regulators. Of the human herpesviruses, cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) both impair the activity of APC/C during their lytic replication through virus-encoded protein kinases. Here, we addressed if the oncogenic Kaposi sarcoma herpesvirus (KSHV) deregulates the activity of APC/C during the lytic replication cycle. To this end, we have used the well-characterized iSLK.219 cell model of KSHV-infection and established a new infection model of primary lymphatic endothelial cells (LEC) infected with a lytically replicating KSHV BAC16 mutant. In contrast to EBV and HCMV, KSHV lytic cycle occurs while the APC/C is active. Moreover, interfering with the APC/C activity did not lead to major changes in the production of infectious virus. We further investigated whether re-replication stress induced by the unscheduled activation of the APC/C-CDH1 affects the number and integrity of the KSHV viral episomes. Deep sequencing of the viral episomes and host chromosomes in the iSLK.219 cells revealed that while distinct regions in the cellular chromosomes were severely affected by the re-replication stress, the integrity of the viral episomes remained unaltered.IMPORTANCEDNA viruses have evolved complex strategies to gain control over the cell cycle. Several of them target APC/C, a key cellular machinery that controls the timely progression of the cell cycle, by either blocking or enhancing its activity. Here, we investigated the activity of APC/C during the lytic replication cycle of KSHV and found that in contrast to its close relatives, EBV and HCMV, the KSHV lytic replication occurs while the APC/C is active. Perturbing the APC/C activity by depleting a core protein or the adaptor proteins of the catalytic domain and hence interfering with the normal cell cycle progression, did not affect the virus replication. This suggests that KSHV has evolved to replicate independently of the APC/C activity and in various cell cycle conditions.