The Pentamer glycoprotein complex inhibits viral Immediate Early transcription during Human Cytomegalovirus infections.

The Pentamer complex of Human Cytomegalovirus (HCMV) consists of the viral glycoproteins gH, gL, UL128, UL130, and UL131 and is incorporated into infectious virions. HCMV strains propagated extensively in vitro in fibroblasts carry UL128, UL130, or UL131 alleles that do not make a functional complex and thus lack Pentamer function. Adding functional Pentamer to such strains decreases virus growth in fibroblasts.

cGAS-STING-TBK1 Signaling Promotes Valproic Acid-Responsive Human Cytomegalovirus Immediate-Early Transcription during Infection of Incompletely Differentiated Myeloid Cells.

Repression of human cytomegalovirus (HCMV) immediate-early (IE) gene expression is a key regulatory step in the establishment and maintenance of latent reservoirs. Viral IE transcription and protein accumulation can be elevated during latency by treatment with histone deacetylase inhibitors such as valproic acid (VPA), rendering infected cells visible to adaptive immune responses. However, the latency-associated viral protein UL138 inhibits the ability of VPA to enhance IE gene expression during infection of incompletely differentiated myeloid cells that support latency.

Triple lysine and nucleosome-binding motifs of the viral IE19 protein are required for human cytomegalovirus S-phase infections.

Herpesvirus genomes are maintained as extrachromosomal plasmids within the nuclei of infected cells. Some herpesviruses persist within dividing cells, putting the viral genome at risk of being lost to the cytoplasm during mitosis because karyokinesis (nuclear division) requires nuclear envelope breakdown. Oncogenic herpesviruses (and papillomaviruses) avoid genome loss during mitosis by tethering their genomes to cellular chromosomes, thereby ensuring viral genome uptake into newly formed nuclei.

NFκB and Cyclic AMP Response Element Sites Mediate the Valproic Acid and UL138 Responsiveness of the Human Cytomegalovirus Major Immediate Early Enhancer and Promoter.

The major immediate early enhancer and promoter (MIEP) of human cytomegalovirus (HCMV) drives the transcription of the immediate early one (IE1) and IE2 genes, whose encoded proteins stimulate productive, lytic replication. The MIEP is activated by the virally encoded and tegument-delivered pp71 protein at the start of lytic infections of fully differentiated cells. Conversely, the MIEP is silenced at the start of latent infections within incompletely differentiated myeloid cells in part because tegument-delivered pp71 is sequestered in the cytoplasm in these cells, but also by viral factors that repress transcription from this locus, including the UL138 protein.

Ataxia Telangiectasia-Mutated Is Activated but Not Required for Productive Autographa californica Multiple Nucleopolyhedrovirus Infection.

Multiplication of the invertebrate DNA baculoviruses activates the host DNA damage response (DDR), which promotes virus DNA replication. DDR signaling is initiated by the host insect's phosphatidylinositol-3 kinase-related kinases (PIKKs), including ataxia telangiectasia-mutated kinase (ATM). Like other PIKKs, ATM phosphorylates an array of host DDR proteins at serine/threonine glutamine (S/TQ) motifs, the result of which leads to cell cycle arrest, DNA repair, or apoptosis.

Serine 13 of the human cytomegalovirus viral cyclin-dependent kinase UL97 is required for regulatory protein 14-3-3 binding and UL97 stability.

The human cytomegalovirus (HCMV) UL97 protein is a conserved herpesvirus protein kinase (CHPK) and a viral cyclin-dependent kinase (v-CDK). However, mechanisms regulating its activity in the context of infection are unknown. Here, we identified several cellular regulatory 14-3-3 proteins as UL97-interacting partners that promote UL97 stability.

Human cytomegalovirus lytic infection inhibits replication-dependent histone synthesis and requires stem loop binding protein function.

Replication-dependent (RD) histones are deposited onto human cytomegalovirus (HCMV) genomes at the start of infection. We examined how HCMV affects the de novo production of RD histones and found that viral infection blocked the accumulation of RD histone mRNAs that normally occurs during the S phase. Furthermore, RD histone mRNAs present in HCMV-infected cells did not undergo the unique 3′ processing required for their normal nuclear export and translation.

Human Cytomegalovirus UL138 Protein Inhibits the STING Pathway and Reduces Interferon Beta mRNA Accumulation during Lytic and Latent Infections.

The cGAS/STING/TBK1 (cyclic guanine monophosphate-AMP synthase/stimulator of interferon genes/Tank-binding kinase 1) innate immunity pathway is activated during human cytomegalovirus (HCMV) productive (lytic) replication in fully differentiated cells and during latency within incompletely differentiated myeloid cells. While multiple lytic-phase HCMV proteins neutralize steps along this pathway, none of them are expressed during latency. Here, we show that the latency-associated protein UL138 inhibits the cGAS/STING/TBK1 innate immunity pathway during transfections and infections, in fully differentiated cells and incompletely differentiated myeloid cells, and with loss of function and restoration of function approaches.

Virology Laboratory Guidelines.

Starting work in a virology research laboratory as a new technician, graduate student, or postdoc can be complex, intimidating, confusing, and stressful. From laboratory logistics to elemental expectations to scientific specifics, there is much to learn. To help new laboratory members adjust and excel, a series of guidelines for working and thriving in a virology laboratory is presented.

An Update on Gender Parity Trends for Invited Speakers at Four Prominent Virology Conference Series.

Historically, men rather than women have been selected for invited speaking positions at the four prominent virology conference series we have followed since the 1980s. However, the low ratio of female representation in most earlier years (20%, 1982-2010) has shown encouraging improvement (37%, 2011-2017), particularly over the last few years (48% from 2018-2020). We describe this promising rise in inclusion and discuss factors that may help perpetuate and extend this overdue transformation towards gender parity.

Human Cytomegalovirus Genomes Survive Mitosis via the IE19 Chromatin-Tethering Domain.

The genomes of DNA tumor viruses regain nuclear localization after nuclear envelope breakdown during mitosis through the action of a viral protein with a chromatin-tethering domain (CTD). Here, we report that the human cytomegalovirus (HCMV) genome is maintained during mitosis by the CTD of the viral IE19 protein. Deletion of the IE19 CTD or disruption of the IE19 splice acceptor site reduced viral genome maintenance and progeny virion formation during infection of dividing fibroblasts, both of which were rescued by IE19 ectopic expression.

Expanding the Known Functional Repertoire of the Human Cytomegalovirus pp71 Protein.

The human cytomegalovirus pp71 protein is packaged within the tegument of infectious virions and performs multiple functions in host cells to prime them for productive, lytic replication. Here we review the known and hypothesized functions of pp71 in regulating proteolysis, infection outcome (lytic or latent), histone deposition, transcription, translation, immune evasion, cell cycle progression, and pathogenesis. We also highlight recent advances in CMV-based vaccine candidates informed by an improved understanding of pp71 function.

Cell Line Models for Human Cytomegalovirus Latency Faithfully Mimic Viral Entry by Macropinocytosis and Endocytosis.

Human cytomegalovirus (HCMV) enters primary CD34 hematopoietic progenitor cells by macropinocytosis, where it establishes latency in part because its tegument-transactivating protein, pp71, remains associated with endosomes and is therefore unable to initiate productive, lytic replication. Here we show that multiple HCMV strains also enter cell line models used to study latency by macropinocytosis and endocytosis. In all latency models tested, tegument-delivered pp71 was found to be colocalized with endosomal markers and was not associated with the seven other cytoplasmic localization markers tested.

The Golgi sorting motifs of human cytomegalovirus UL138 are not required for latency maintenance.

Human cytomegalovirus (HCMV) establishes latency within incompletely differentiated cells of the myeloid lineage. The viral protein UL138 participates in establishing and maintaining this latent state. UL138 has multiple functions during latency that include silencing productive phase viral gene transcription and modulating intracellular protein trafficking.

Human Cytomegalovirus Enters the Primary CD34 Hematopoietic Progenitor Cells Where It Establishes Latency by Macropinocytosis.

Viral entry is targeted by immunological and pharmacological measures to inhibit viral infection. Human cytomegalovirus (HCMV) entry into cells where it initiates productive infection has been well studied, but its entry into cell types where it establishes latency has not. Therefore, we examined the entry of HCMV into CD34 hematopoietic progenitor cells where the virus establishes latency.

The Membrane-Spanning Peptide and Acidic Cluster Dileucine Sorting Motif of UL138 Are Required To Downregulate MRP1 Drug Transporter Function in Human Cytomegalovirus-Infected Cells.

The human cytomegalovirus (HCMV) UL138 protein downregulates the cell surface expression of the multidrug resistance-associated protein 1 (MRP1) transporter. We examined the genetic requirements within UL138 for MRP1 downregulation. We determined that the acidic cluster dileucine motif is essential for UL138-mediated downregulation of MRP1 steady-state levels and inhibition of MRP1 efflux activity.

A cancer-associated Epstein-Barr virus BZLF1 promoter variant enhances lytic infection.

Latent Epstein-Barr virus (EBV) infection contributes to both B-cell and epithelial-cell malignancies. However, whether lytic EBV infection also contributes to tumors is unclear, although the association between malaria infection and Burkitt lymphomas (BLs) may involve excessive lytic EBV replication. A particular variant of the viral promoter (Zp) that controls lytic EBV reactivation is over-represented, relative to its frequency in non-malignant tissue, in EBV-positive nasopharyngeal carcinomas and AIDS-related lymphomas.

Human Cytomegalovirus Productively Replicates in Undifferentiated Oral Epithelial Cells.

Human cytomegalovirus (HCMV) productive replication is most often studied in fibroblasts. , fibroblasts amplify viral titers, but transmission and pathogenesis require the infection of other cell types, most notably epithelial cells. , the study of HCMV infection of epithelial cells has been almost exclusively restricted to ocular epithelial cells.

HCMV Assembly Is Totally Tubular.

Microtubules are normally organized at centrosomes, but other sites can also serve as microtubule organizing centers (MTOCs). In this issue of Developmental Cell, Procter et al. (2018) show that the human cytomegalovirus virion assembly compartment acts as a dynamic Golgi-derived MTOC where EB3 nucleates microtubules and regulates infectious virion production.

Direct Substrate Identification with an Analog Sensitive (AS) Viral Cyclin-Dependent Kinase (v-Cdk).

Viral cyclin-dependent kinases (v-Cdks) functionally emulate their cellular Cdk counterparts. Such viral mimicry is an established phenomenon that we extend here through chemical genetics. Kinases contain gatekeeper residues that limit the size of molecules that can be accommodated within the enzyme active site.

Phosphorylation of transcriptional regulators in the retinoblastoma protein pathway by UL97, the viral cyclin-dependent kinase encoded by human cytomegalovirus.

Human cytomegalovirus (HCMV) encodes a viral cyclin-dependent kinase (v-CDK), the UL97 protein. UL97 phosphorylates Rb, p107 and p130, thereby inactivating all three retinoblastoma (Rb) family members. Rb proteins function through regulating the activity of transcription factors to which they bind.

Human Cytomegalovirus-Infected Glioblastoma Cells Display Stem Cell-Like Phenotypes.

Glioblastoma multiforme (GBM) is the most common brain tumor in adults. Human cytomegalovirus (HCMV) genomes are present in GBM tumors, yielding hope that antiviral treatments could prove therapeutic and improve the poor prognosis of GBM patients. We discovered that GBM cells infected with HCMV display properties of cancer stem cells.

Gender Parity Trends for Invited Speakers at Four Prominent Virology Conference Series.

Scientific conferences are most beneficial to participants when they showcase significant new experimental developments, accurately summarize the current state of the field, and provide strong opportunities for collaborative networking. A top-notch slate of invited speakers, assembled by conference organizers or committees, is key to achieving these goals. The perceived underrepresentation of female speakers at prominent scientific meetings is currently a popular topic for discussion, but one that often lacks supportive data.

Human cytomegalovirus-encoded viral cyclin-dependent kinase (v-CDK) UL97 phosphorylates and inactivates the retinoblastoma protein-related p107 and p130 proteins.

The human cytomegalovirus (HCMV)-encoded viral cyclin-dependent kinase (v-CDK) UL97 phosphorylates the retinoblastoma (Rb) tumor suppressor. Here, we identify the other Rb family members p107 and p130 as novel targets of UL97. UL97 phosphorylates p107 and p130 thereby inhibiting their ability to repress the E2F-responsive E2F1 promoter.