Biology subjects

Parkins, C.

Publications and source records attributed to Parkins, C..

3 recordsLinked to original sources

bioRxiv2025

The human cytomegalovirus chemokine binding protein UL22A is necessary for efficient reactivation from latency in CD34+ hematopoietic progenitor cells.

Herpesviruses and Poxviruses encode secreted chemokine binding proteins that prevent the interaction between chemokines and their cognate G protein coupled receptors to alter chemotactic gradients and intracellular signaling pathways. Human cytomegalovirus (HCMV) encodes the secreted protein UL22A (formerly UL21.5), which is described as a CCL5 (RANTES) binding protein and requires sulfation at two tyrosine residues (Y65 and Y69) for efficient RANTES interaction. In this report, we show that the UL22A protein, and the UL22A Y65 and Y69 residues are necessary for efficient HCMV reactivation from latency in CD34+ hematopoietic progenitor cells and that UL22A expression is essential for reactivation in a humanized mouse model of latency. However, RANTES neutralization is not sufficient to complement the in vitro reactivation defect of UL22A mutant viruses. These data suggest that UL22A plays an important role in latency, possibly through interactions with additional chemokines or other types of ligands via its tyrosine residues, in order to mediate efficient HCMV reactivation. IMPORTANCEHCMV is a ubiquitous herpesvirus that infects 60-90% of the population worldwide. In immunocompetent individuals, primary infection is asymptomatic and results in lifelong latent infection in CD34+ hematopoietic progenitor cells (HPCs). Viral reactivation remains a major complication for immunosuppressed individuals, but current therapeutics targeting HCMV replication show significant toxicity. Thus, a better understanding of the mechanisms controlling latency and reactivation is necessary to develop new therapeutics targeting these stages of the HCMV lifecycle. We show that virus lacking the HCMV chemokine binding protein UL22A is incapable of efficient reactivation in CD34+ HPCs and in vivo. UL22A tyrosine residues important for interaction with the chemokine RANTES are necessary for reactivation. However, neutralizing RANTES does not complement the reactivation defect of UL22A mutant viruses, demonstrating that UL22A has functions other than RANTES binding. Together, our results reveal a novel role for UL22A in HPCs and a new understanding of UL22A-chemokine interactions.

microbiology↗

bioRxiv2025

HCMV promotes viral reactivation through the coordinated regulation of Notch signaling by UL8 and miR-UL36

Human cytomegalovirus (HCMV) establishes latency in CD34+ hematopoietic progenitor cells (HPCs), where reactivation is intimately linked to cellular differentiation. We demonstrate that the Notch signaling pathway, a key regulator of stem cell maintenance and differentiation, functions as a barrier to HCMV reactivation. Two viral gene products, UL8 and miR-UL36, modulate this pathway during reactivation. UL8 promotes degradation of the Notch3 receptor via the endosomal/lysosomal pathway, dependent on two tyrosine-based motifs (Y305/314) in its cytoplasmic tail. A UL8 mutant lacking these motifs fails to degrade Notch3, resulting in sustained Notch signaling and impaired reactivation in vitro and in humanized mice. Similarly, miR-UL36 reduces expression of Notch3 and the Notch transcription factor Recombination Signal Binding Protein For Immunoglobulin Kappa J Region (RBPJ), suppressing Notch signaling. Deletion of miR-UL36 inhibits reactivation, but this defect, like that of the UL8 mutant, can be rescued by pharmacologic Notch inhibition. Thus, HCMV employs multiple gene products to suppress Notch signaling and promote conditions conducive to reactivation. These findings reveal how HCMV manipulates host differentiation pathways to control latency and suggest therapeutic strategies to prevent viral recurrence in immunocompromised patients. ImportanceHuman cytomegalovirus (HCMV) establishes lifelong latency, posing significant risks to transplant recipients and other immunocompromised individuals. Reactivation depends on progenitor cell differentiation, yet the viral mechanisms governing this process remain unclear. We identify Notch signaling as a major inhibitory pathway to reactivation and show that HCMV uses UL8 and miR-UL36 to suppress this pathway. UL8 degrades Notch3, while miR-UL36 downregulates Notch3 and RBPJ, together reducing Notch signaling and enabling reactivation. Mutant viruses lacking these regulators fail to reactivate efficiently, but this can be reversed by pharmacological inhibition of Notch. These findings establish Notch pathway suppression as a critical viral strategy for reactivation and highlight potential therapeutic targets for preventing HCMV disease.

microbiology↗

bioRxiv2023

UL135 and UL136 Epistasis Controls Reactivation of Human Cytomegalovirus

Human cytomegalovirus (HCMV) is beta herpesvirus that persists indefinitely in the human host through a protracted, latent infection. The polycistronic UL133-UL138 gene locus of HCMV encodes genes regulating latency and reactivation. While UL138 is pro-latency, restricting virus replication in CD34+ hematopoietic progenitor cells (HPCs), UL135 overcomes this restriction for reactivation. By contrast, UL136 is expressed with later kinetics and encodes multiple protein isoforms with differential roles in latency and reactivation. Like UL135, the largest UL136 isoform, UL136p33, is required for reactivation from latency in hematopoietic cells. Furthermore, UL136p33 is unstable, and its instability is important for the establishment of latency and sufficient accumulation of UL136p33 is a checkpoint for reactivation. We hypothesized that stabilizing UL136p33 might overcome the requirement of UL135 for reactivation. To test this, we generated recombinant viruses lacking UL135 that expressed a stabilized variant of UL136p33. Stabilizing UL136p33 did not impact replication of the UL135-mutant virus in fibroblasts. However, in the context of infection in hematopoietic cells, stabilization of UL136p33 strikingly compensated for the loss of UL135, resulting in increased replication in CD34+ HPCs and in humanized NOD-scid IL2R{gamma}cnull (NSG) mice. This finding suggests that while UL135 is essential for reactivation, it functions at steps preceding the accumulation of UL136p33 and that stabilized expression of UL136p33 largely overcomes the requirement for UL135 in reactivation. Taken together, our genetic evidence indicates an epistatic relationship between UL136p33 and UL135 whereby UL135 may initiate events early in reactivation that will result in the accumulation of UL136p33 to a threshold required for productive reactivation. SIGNIFICANCEHuman cytomegalovirus (HCMV) is one of nine human herpesviruses and a significant human pathogen. While HCMV establishes a life-long latent infection that is typically asymptomatic in healthy individuals, its reactivation from latency can have devastating consequences in the immune compromised. Defining virus-host and virus-virus interactions important for HCMV latency, reactivation and replication is critical to defining the molecular basis of latent and replicative states and in controlling infection and CMV disease. Here we define a genetic relationship between two viral genes in controlling virus reactivation from latency using primary human hematopoietic progenitor cell and humanized mouse models.

microbiology↗