Multiple Lytic Origins of Replication Are Required for Optimal Gammaherpesvirus Fitness In Vitro and In Vivo

Abstract

An unresolved question in herpesvirus biology is why some herpesviruses contain more than one lytic origin of replication (oriLyt). Using murine gammaherpesvirus 68 (MHV-68) as model virus containing two oriLyts, we demonstrate that loss of either of the two oriLyts was well tolerated in some situations but not in others both in vitro and in vivo. This was related to the cell type, the organ or the route of inoculation. Depending on the cell type, different cellular proteins, for example Hexim1 and Rbbp4, were found to be associated with oriLyt DNA. Overexpression or downregulation of these proteins differentially affected the growth of mutants lacking either the left or the right oriLyt. Thus, multiple oriLyts are required to ensure optimal fitness in different cell types and tissues.

RTA Occupancy of the Origin of Lytic Replication during Murine Gammaherpesvirus 68 Reactivation from B Cell Latency

“…Similar to EBV and KSHV [57,58,59], MHV68 contains two functional oriLyt sequences that each serve as sites for initiating viral DNA replication [60,61]. The oriLyt-L and oriLyt-R have non-redundant roles for replication in specific cell types and tissues in vivo [61]. Binding of the EBV Zta protein to the oriLyt is essential for the initiation of DNA replication [62].…”

Herpesviruses and Their Host Cells: A Successful Liaison

“…HCMV codes for a gH/gL/gO complex which drives infection of cells expressing platelet-derived growth factor receptor alpha (PDGFR-/) [16], and for a gH/gL/pUL(128,130,131A) complex which drives infection of most PDGFR-/-negative cells through a still unknown receptor. In cell culture, fibroblasts infected with HCMV release virions with high or low amounts of gH/gL/pUL Noncoding RNAs (including miRNAs) [44,45,47] Origins of lytic replication (oriLyts) [51] Antiapoptotic genes [70] Genes counteracting host cell defense mechanisms (immune evasion genes) [71][72][73][74][75][76][77][78] Genes influencing cell cycle or proliferation [79,80] Genes interfering with epigenetic silencing [63,81] Cellular (host) factors Refs…”

“…, and signaling coreceptors [67,82] Noncoding RNAs (including miRNAs) [41,42,48] Proteins interacting with oriLyts [51] Interferons and other cytokines [30,[32][33][34] Sensors of viral infection [23,83,84] Cell cycle proteins [62,85,86] Proteins regulating apoptosis [87][88][89][90] Transcription factors [91] DNA damage response proteins [5] Proteins involved in epigenetic gene regulation including chromatin assembly, histone modifications[ 3 _ T D $ D I F F ] , and DNA methylation [21][22][23][24][25][26][27][28]63,[92][93][94][95][96][97][98] Autophagy and xenophagy [99][100][101] Ubiquitination and NEDDylation [102][103][104][105] Chaperones [65] Post-translational modification proteins …”

“…While some herpesviruses, for example HCMV, have a single oriLyt, others such as MHV-68 have multiple oriLyts [49,50]. In a recent study, the role of the oriLyts of MHV-68 was examined [51]. The working hypothesis was that the presence of two oriLyts can overcome cell-type-specific restrictions of lytic replication by cellular proteins.…”

B cells latently infected with murine gammaherpesvirus 68 (MHV‐68) are present in the mouse thymus–A step toward immune evasion?

“…To address whether latently infected B cells can indeed be found in the thymus, we made use of murine gammaherpesvirus 68 (MHV‐68), a well‐established mouse model to study the host control of gammaherpesviruses . First, we analyzed both the spleen and the thymus of mice infected for 17 days, when latency is established , for the presence of latently infected B cells . As shown in Fig.…”