HCMV latency: what regulates the regulators?

Elder, Elizabeth; Sinclair, John

doi:10.1007/s00430-019-00581-1

Cited by 64 publications

(60 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It has long been assumed that MIE gene expression that supports reactivation of the viral lytic cycle results from derepression of the MIEP, and changes in transcription factor binding and chromatin have been detected at the MIEP upon reactivation (29)(30)(31)(32)(33)(34)(35). While our data do not preclude a role for the MIEP, iP-derived transcripts are the predominant drivers of viral IE gene re-expression following a reactivation stimulus (Fig.…”

Section: Discussionmentioning

confidence: 52%

Alternative promoters drive human cytomegalovirus reactivation from latency

Collins-McMillen

Rak

Buehler

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Reactivation from latency requires reinitiation of viral gene expression and culminates in the production of infectious progeny. The major immediate early promoter (MIEP) of human cytomegalovirus (HCMV) drives the expression of crucial lytic cycle transactivators but is silenced during latency in hematopoietic progenitor cells (HPCs). Because the MIEP has poor activity in HPCs, it is unclear how viral transactivators are expressed during reactivation. It has been presumed that viral gene expression is reinitiated via de-repression of the MIEP. We demonstrate that immediate early transcripts arising from reactivation originate predominantly from alternative promoters within the canonical major immediate early locus. Disruption of these intronic promoters results in striking defects in re-expression of viral genes and viral genome replication in the THP-1 latency model. Furthermore, we show that these promoters are necessary for efficient reactivation in primary CD34 + HPCs. Our findings shift the paradigm for HCMV reactivation by demonstrating that promoter switching governs reactivation from viral latency in a context-specific manner.human cytomegalovirus | latency | reactivation R eactivation of latent human cytomegalovirus (HCMV) infection poses a life-threatening risk to immunocompromised individuals, such as stem cell or organ transplant recipients (1). While the HCMV replicative cycle has been studied extensively, our understanding of the mechanisms controlling the entry into and exit from latency is far from complete.During productive infection, the HCMV genome is transcribed in a temporal cascade composed of three kinetic classes of gene expression designated as immediate early (IE), early, and late (2). The IE proteins, in particular IE1-72 kilodalton (kDa) and IE2-86 kDa proteins, referred to as IE1 and IE2, play critical roles in initiating the HCMV lytic cycle by transactivating the expression of cellular and viral genes and suppressing the innate immune response (3). During latency, IE gene expression is repressed, resulting in diminished viral gene expression and the absence of productive replication (4). Signals that stimulate reactivation induce IE gene expression to allow reentry into the viral replicative cycle (5), and this de-repression of IE genes is considered a pivotal event controlling the switch between latent and reactivated states.The major immediate early promoter (MIEP) is a powerful promoter in cells permissive for lytic HCMV replication and drives high level expression of mRNAs encoding IE1 (UL123) and IE2 (UL122) (6-9). In cell types that support HCMV latency, however, such as CD34 + human progenitor cells (HPCs) and CD14 + monocytes, MIEP activity is diminished (10-12). Because re-expression of UL122 and UL123 is required for reactivation (13-15), it has been presumed that de-repression of the MIEP is critical to reinitiate the viral lytic cycle. However, the origin of UL123 and UL122 transcripts during HCMV reactivation has not been formally defined. ResultsRe-Expression of UL123 ...

show abstract

Section: Discussionmentioning

confidence: 52%

Alternative promoters drive human cytomegalovirus reactivation from latency

Collins-McMillen

Rak

Buehler

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…While US28 is dispensable for lytic replication in vitro 76,77 , it is essential for the establishment and maintenance of HCMV latency in early myeloid lineage cells 19,21,23,25 . This is attributable, in part, to the ability of US28 to suppress the major immediate early promoter; a US28 function specific for undifferentiated myeloid cells 18,21,23,25 .…”

Section: Discussionmentioning

confidence: 99%

“…However, we predict that some of the signalling-independent changes driven by US28 could also be important for HCMV latency, since these changes included alterations in several cell-surface molecules such as co-stimulatory molecule CD82, adhesion molecule CD44, and in receptor tyrosine kinase FLT3. The latter two cellular factors are implicated in myeloid cell differentiation, which is intimately linked with HCMV latency and reactivation 18,72,78–80 . As such, modulating these cell-surface molecules could help to control interactions with immune effectors and cellular differentiation-linked reactivation.…”

Section: Discussionmentioning

confidence: 99%

“…A key hallmark of latency is the relative suppression of IE gene expression 1,2,12–14 , which is controlled by the major immediate early promoter 15–17 , and the subsequent lack of infectious virion production. The establishment of latency via MIEP repression in early myeloid lineage cells requires both host and viral factors 18 . One viral factor that suppresses MIEP activity is the G-protein coupled receptor (GPCR) US28, a virally encoded chemokine receptor homologue, which is expressed de novo during latency as well as being delivered to cells with the incoming virion 19–24 and this incoming viral US28 is functional 25 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Interferon-responsive genes are targeted during the establishment of human cytomegalovirus latency

Krishna

Williamson

Lim

et al. 2019

Preprint

Self Cite

View full text Add to dashboard Cite

12Human cytomegalovirus (HCMV) latency is an active process which remodels the latently infected 13 cell to optimise latent carriage and reactivation. This is achieved, in part, through the expression of 14 viral genes, including the G-protein coupled receptor US28. Here, we use an unbiased proteomic 15 screen to assess changes in host proteins induced by US28, revealing that interferon-inducible genes 16 are downregulated by US28. We validate that MHC Class II and two PYHIN proteins, MNDA and 17 IFI16, are downregulated during experimental latency in primary human CD14 + monocytes. We find 18 that IFI16 is targeted rapidly during the establishment of latency in a US28-dependent manner, but 19 only in undifferentiated myeloid cells, a natural site of latent carriage. Finally, by overexpressing 20 IFI16, we show that IFI16 can activate the viral major immediate early promoter and immediate early 21 2 gene expression during latency via NF-κB, a function which explains why downregulation of IFI16 22 during latency is advantageous for the virus. 23 Importance 24 Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus which infects 50-100% of humans 25 worldwide. HCMV causes a lifelong subclinical infection in immunocompetent individuals, but is a 26 serious cause of mortality and morbidity in the immunocompromised and in neonates. In particular, 27 reactivation of HCMV in the transplant setting is a major cause of transplant failure and related 28 disease. Therefore, a molecular understanding of HCMV latency and reactivation could provide 29 insights into potential ways to target the latent viral reservoir in at-risk patient populations. 30 31 both host and viral factors 18 . One viral factor that suppresses MIEP activity is the G-protein coupled 46 receptor (GPCR) US28, a virally encoded chemokine receptor homologue, which is expressed de 47 novo during latency as well as being delivered to cells with the incoming virion 19-24 and this 48 incoming viral US28 is functional 25 . US28 modulates the signalling pathways of early myeloid cells; it 49 attenuates MAP kinases, NF-κB, and c-fos, whilst activating STAT3 and iNOS 21,23,25 . All of these 50 contribute to the repression of MIEP activity. This US28-mediated signalling is so critical to latency 51 that US28-deleted viruses, or the loss of G-protein coupling by the US28 mutant R129A, result in lytic 52 infection of undifferentiated myeloid cells 19,21,23,25 . Furthermore, when examined, these US28-53 mediated effects on cell signalling did not occur during lytic infection or in permissive cells 21 , 54 implying that US28 represses the MIEP during latency but does not impair reactivation following 55 cellular differentiation. This is reflective of the cell type-specific nature of US28-mediated signalling 56 21,26 . 57Since US28 can modulate all these pathways and control the MIEP, we hypothesised that US28 58 would also cause changes in host protein expression. Here, we perform a proteomic screen 59 comparing host cell protein abundance in myelomonocytic TH...

show abstract

“…This underscores the need to better understand these phases of viral infection 34 to prevent disease and improve patient outcomes. 35 36 Our current understanding of the biological mechanisms controlling latency and reactivation 37 remain incomplete, though work from many labs have detailed the importance of both host and viral 38 factors in these processes (Collins-McMillen et al, 2018;Elder and Sinclair, 2019). We and others 39 have shown the viral G protein-coupled receptor (GPCR) US28 is required for viral latency (Humby 40 and O'Connor, 2015; Wu and Miller, 2016; Krishna et al, 2017;Krishna et al, 2019).…”

Section: Introduction 29mentioning

confidence: 99%

The Requirement For US28 During Cytomegalovirus Latency Is Independent Of US27 And US29 Gene Expression

Krishna

Wass

Sridharan

et al. 2020

Preprint

View full text Add to dashboard Cite

AbstractThe ability to establish a latent infection with periodic reactivation events ensures herpesviruses, like human cytomegalovirus (HCMV), lifelong infection and serial passage. The host-pathogen relationship throughout HCMV latency is complex, though both cellular and viral factors influence the equilibrium between latent and lytic infection. We and others have shown one of the viral-encoded G protein-coupled receptors, US28, is required for HCMV latency. US28 potentiates signals both constitutively and in response to ligand binding, and we previously showed deletion of the ligand binding domain or mutation of the G protein-coupling domain results in the failure to maintain latency similar to deletion of the entire US28 open reading frame (ORF). Interestingly, a recent publication detailed an altered phenotype from that previously reported, showing US28 is required for viral reactivation rather than latency, suggesting the US28 ORF deletion impacts transcription of the surrounding genes. Here, we show an independently generated US28-stop mutant, like the US28 ORF deletion mutant, fails to maintain latency in hematopoietic cells. Further, we found US27 and US29 transcription in each of these mutants was comparable to their expression during wild type infection, suggesting neither US28 mutant alters mRNA levels of the surrounding genes. Finally, infection with a US28 ORF deletion virus expressed US27 protein comparable to its expression following wild type infection. In sum, our new data strongly support previous findings from our lab and others, detailing a requirement for US28 during HCMV latent infection.

show abstract

HCMV latency: what regulates the regulators?

Cited by 64 publications

References 77 publications

Alternative promoters drive human cytomegalovirus reactivation from latency

Alternative promoters drive human cytomegalovirus reactivation from latency

Interferon-responsive genes are targeted during the establishment of human cytomegalovirus latency

The Requirement For US28 During Cytomegalovirus Latency Is Independent Of US27 And US29 Gene Expression

Contact Info

Product

Resources

About