Abstract:E2F transcription factors play pivotal roles in controlling the expression of genes involved in cell-cycle progression. Different viruses affect E2F1/retinoblastoma (Rb) interactions by diverse mechanisms releasing E2F1 from its suppressor Rb, enabling viral replication. We show that in T cells infected with human herpesvirus 6A (HHV-6A), the E2F1 protein and its cofactor DP1 increased, whereas the Rb protein underwent massive degradation without hyperphosphorylation at three sites known to control E2F/Rb asso… Show more
“…Roseoloviruses push the cell cycle into G2/M, presumably to ramp up cellular processes that promote DNA replication [46]. Virally-induced degradation of Rb and activation of E2F1 further benefits HHV-6A and HHV-6B by enhancing the expression of some lytic genes [47]. Many roseolovirus gene products inhibit both innate immune responses (U20, IE1) and adaptive immune responses (U21), and interfere with cell death (U19, U20, DR6) and T cell signaling (U21, U54) [48].…”
Human herpesviruses 6A, −6B, and −7 (HHV-6A, −6B, and −7) are classified within the roseolovirus genus of the betaherpesvrus subfamily. Most humans likely harbor at least two of these large DNA viruses, and 1% of humans harbor germline chromosomally integrated HHV-6A or HHV-6B genomes. Differences at the genetic level manifest as distinct biologic properties during infection and disease. We provide a brief synopsis of roseolovirus replication and highlight the unique properties of their lifecycle and what is known about the viral gene products that mediate these functions. In the nearly 30 years since their discovery, we have only begun to unlock the molecular strategies these highly evolved pathogens employ to establish and maintain chronic infections in humans.
“…Roseoloviruses push the cell cycle into G2/M, presumably to ramp up cellular processes that promote DNA replication [46]. Virally-induced degradation of Rb and activation of E2F1 further benefits HHV-6A and HHV-6B by enhancing the expression of some lytic genes [47]. Many roseolovirus gene products inhibit both innate immune responses (U20, IE1) and adaptive immune responses (U21), and interfere with cell death (U19, U20, DR6) and T cell signaling (U21, U54) [48].…”
Human herpesviruses 6A, −6B, and −7 (HHV-6A, −6B, and −7) are classified within the roseolovirus genus of the betaherpesvrus subfamily. Most humans likely harbor at least two of these large DNA viruses, and 1% of humans harbor germline chromosomally integrated HHV-6A or HHV-6B genomes. Differences at the genetic level manifest as distinct biologic properties during infection and disease. We provide a brief synopsis of roseolovirus replication and highlight the unique properties of their lifecycle and what is known about the viral gene products that mediate these functions. In the nearly 30 years since their discovery, we have only begun to unlock the molecular strategies these highly evolved pathogens employ to establish and maintain chronic infections in humans.
“…Relapse of CIU had been documented in these patients on discontinuation of therapy, confirming that the underlying disease was still present. An additional patient described anonymously with CIU and autoimmune thyroiditis had previously signed a written consent for participation in a retrospective chart review and also for ‘off‐label use’ of valacylovir (Valtrex), as urticaria associated with autoimmune thyroid disease may be a candidate for further prospective placebo‐controlled study of both conventional and novel anti‐viral therapy . Because omalizumab therapy was started prior to Food and Drug Administration (FDA) approval of omalizumab for CIU, all omalizumab‐treated patients had a co‐diagnosis of asthma or wheezing associated with CIU, and some also had autoimmune thyroid disease, as noted, but patients were otherwise healthy.…”
SummaryAcute infection with viral pathogens in the herpesviridae family can trigger acute urticaria, and reactivation of herpesviridae is associated with cutaneous urticarial-like syndromes such as drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DRESS). Reactivation of latent herpesviridae has not been studied systematically in chronic idiopathic/spontaneous urticaria (CIU). This review proposes that CIU is an inflammatory disorder with autoimmune features (termed 'CVU' for chronic viral urticaria), based on serology consistent with the hypothesis that reactivation of a latent herpesvirus or -viruses may play a role in CIU. Serology obtained from a cohort of omalizumab (Xolair)-dependent patients with severe CIU was consistent with previous HHV-6 infection, persistent viral gene expression and replication. CIU patients also exhibited serological evidence of increased immune response to HHV-4 (Epstein-Barr virus, or EBV) but not all CIU patients were infected with EBV. These observations, combined with case reports of CIU response to anti-viral therapy, suggest that HHV-6, possibly interacting with HHV-4 in cutaneous tissues, is a candidate for further prospective study as a co-factor in CIU.
“…HHV-6 alters the E2F1/Rb pathway and E2F1 localization and causes cell-cycle arrest in infected cells [ 24 ]. This also causes an elevation in levels of the transcription factor E2F1, which promotes expression of genes important for viral DNA synthesis, such as U27 and U79 [ 24 , 29 ]. During HHV-6B infection, the majority of cellular p53 is inactivated and stabilized in the cytoplasm, most likely due to a reduction in p53 degradation [ 30 ].…”
The human herpesvirus-6 (HHV-6) infection induces cell-cycle arrest. In this study, we found that the HHV-6-encoded U14 protein induced cell-cycle arrest at G2/M phase via an association with the cellular protein EDD, a mediator of DNA-damage signal transduction. In the early phase of HHV-6 infection, U14 colocalized with EDD dots in the nucleus, and similar colocalization was also observed in cells transfected with a U14 expression vector. When the carboxyl-terminal region of U14 was deleted, no association of U14 and EDD was observed, and the percentage of cells in G2/M decreased relative to that in cells expressing wild-type U14, indicating that the C-terminal region of U14 and the U14–EDD association are critical for the cell-cycle arrest induced by U14. These results indicate that U14 is a G2/M checkpoint regulator encoded by HHV-6.
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