Biology subjects

Munger, K.

Publications and source records attributed to Munger, K..

4 recordsLinked to original sources

bioRxiv2026

Differentiation-independent Activation of HPV Genome Replication by the lncRNA DINO

Human papillomaviruses (HPV) rely on multiple host cell factors to replicate the viral genome, yet the contribution of host long noncoding RNAs (lncRNAs) to viral genome maintenance and amplification in the productive life cycle remains poorly understood. In this study, we show that the lncRNA DINO is a driver of HPV DNA replication. DINO levels increase during keratinocyte differentiation and ectopic expression of DINO promotes both HPV genome replication and the formation of replication foci, and this is independent of keratinocyte differentiation signals. Ectopic DINO expression increases select early viral transcript levels including E1^E4, E1, and E2. Notably, DINOs subcellular localization is also context-dependent: during DNA damage DINO is predominantly cytoplasmic, but during keratinocyte differentiation nuclear retention is observed. This differential localization suggests that DINO has distinct functional roles in keratinocyte differentiation and HPV biology. Our findings highlight DINO as a lncRNA that promotes HPV genome replication and suggest that lncRNAs may play underappreciated roles in host-virus interactions. This work provides a foundation for further exploration of lncRNAs as potential therapeutic targets in HPV-associated diseases. ImportanceHuman papillomaviruses (HPVs) are the causative agents of many anogenital tract and oral cancers, yet the host factors that trigger and support viral genome replication during the productive life cycle are incompletely understood. This study identifies the long noncoding RNA DINO as a host regulator that promotes HPV DNA replication, replication focus formation, and early viral gene expression independently of keratinocyte differentiation. We further show that DINO exhibits context-dependent subcellular localization, suggesting distinct functional roles in cellular stress responses and HPV biology. These findings reveal an underappreciated role for host lncRNAs in virus-host interactions and provide new insight into cellular pathways that support HPV genome replication.

microbiology↗

bioRxiv2026

Inactivation of the RB1 and PTPN14 tumor suppressors cooperatively enables the carcinogenic activity of the human papillomavirus E7 oncoprotein

High-risk human papillomavirus (HPV) E7 proteins bind and inactivate host cellular tumor suppressors and are essential for the immortalization of primary human keratinocytes. E7 proteins from high- and low-risk HPV genotypes bind directly to at least two tumor suppressors, RB1 and PTPN14, and inactivate both. We previously characterized mutations in high-risk HPV E7 proteins that selectively abrogate the ability of E7 to bind either RB1 or PTPN14. Here, we established a genetic complementation system using the E7 mutants defective for binding to RB1 or PTPN14. Neither mutant alone could extend the lifespan of primary keratinocytes. When expressed together, the mutants could, like wild-type high-risk HPV E7, extend keratinocyte lifespan. Both high- and low-risk E7 reduced PTPN14 protein levels and reduced expression of keratinocyte differentiation genes, whereas only high-risk E7 reduced steady-state RB1 levels and induced E2F-dependent genes. Depletion of either RB1 or PTPN14 could cooperate with low-risk HPV6 E7 to extend keratinocyte lifespan. Our findings advance the model that inactivation of at least two tumor suppressors is required for the lifespan extension activity of high-risk HPV E7. SignificanceInactivation of the retinoblastoma tumor suppressor (RB1) is necessary but insufficient for HPV E7-mediated immortalization of human cells. In addition to inactivating RB1, HPV E7 proteins also target for degradation PTPN14, a tumor suppressor and inhibitor of the YAP1 oncoprotein. We report genetic complementation experiments demonstrating that RB1 inactivation and PTPN14 inactivation are separate activities of E7. Either depletion of RB1 or PTPN14 can confer lifespan extension activity on a low-risk HPV E7. These findings redefine our understanding of E7 transforming activity. The predominant difference between high- and low-risk E7 is their ability to degrade RB1, but inactivation of both tumor suppressors is required for E7 activity. Targeting either E7/RB1 or E7/PTPN14 could be of therapeutic benefit.

microbiology↗

bioRxiv2023

The HPV8 E6 protein targets the Hippo and Wnt signaling pathways as part of its arsenal to restrain keratinocyte differentiation

Infections with {beta}-genus HPVs cause hyperplastic cutaneous lesions. In individuals with the rare hereditary skin disease, epidermodysplasia verruciformis, such lesions can progress to cutaneous squamous cell carcinomas (cSCC). {beta}-HPV infections may also underlie cSCC development in chronically immunosuppressed individuals. Despite their prevalence and disease association, these viruses are not as well studied as the cancer-associated high-risk -genus HPVs. HPV-associated lesions are characterized by a marked expansion of dividing, basal-like, poorly differentiated viral cells that contain viral genomes. This reflects the ability of HPVs to inhibit epithelial cell differentiation which is likely driven by the need to establish and maintain long-term viral infections in basal-like epithelial cells. Remarkably, the {beta}-HPVs accomplish this by targeting different cellular effectors than the -genus HPVs. It was previously reported that the HPV8 E6 protein restrains epithelial cell differentiation by inhibiting Notch and TGF-{beta} signaling. Here we report that the HPV8 E6 protein can subvert Hippo signaling by activating TEAD transcriptional programs that inhibit the expression of keratinocyte differentiation markers. Moreover, we determined that HPV8 E6 can interfere with gene expression programs triggered by Wnt signaling by binding to the {beta}-catenin-associated transcriptional co-activator BCL9L and that this also serves to restrain the expression of epithelial differentiation markers. Hence the HPV8 E6 protein has evolved a remarkably large array of mechanisms to subvert the differentiation program of the infected epithelial cells. IMPORTANCEHuman papillomaviruses (HPVs) infect basal epithelial cells and cause a dramatic expansion of basal-like, proliferative cells. This reflects the ability of papillomaviruses to delay keratinocyte differentiation thereby maintaining aspects of the basal cell identity of persistently infected cells. This may enable papillomaviruses to establish and maintain long-term infections in squamous epithelial tissues. Previous work has revealed that the ability of {beta}-HPV8 E6 protein to inhibit NOTCH and TGF-{beta} signaling importantly contributes to this activity. Here we present evidence that HPV8 E6 also subverts Hippo and Wnt signaling and that these activities also aid in restraining keratinocyte differentiation.

microbiology↗

bioRxiv2018

PTPN14 Degradation by High-Risk Human Papillomavirus E7 Limits Keratinocyte Differentiation and Contributes to HPV-Mediated Oncogenesis

High-risk human papillomavirus (HPV) E7 proteins enable oncogenic transformation of HPV-infected cells by inactivating host cellular proteins. High-risk but not low-risk HPV E7 target PTPN14 for proteolytic degradation, suggesting that PTPN14 degradation may be related to their oncogenic activity. HPV infects human keratinocytes but the role of PTPN14 in keratinocytes and the consequences of PTPN14 degradation are unknown. Using an HPV16 E7 variant that can inactivate RB1 but cannot degrade PTPN14 we found that high-risk HPV E7-mediated PTPN14 degradation impairs keratinocyte differentiation. Deletion of PTPN14 from primary human keratinocytes decreased keratinocyte differentiation gene expression. Related to oncogenic transformation, both HPV16 E7-mediated PTPN14 degradation and PTPN14 deletion promoted keratinocyte survival following detachment from a substrate. PTPN14 degradation contributed to high-risk HPV E6/E7-mediated immortalization of primary keratinocytes and HPV-positive but not HPV-negative cancers exhibit a gene expression signature consistent with PTPN14 inactivation. We find that PTPN14 degradation impairs keratinocyte differentiation and propose that this contributes to high-risk HPV E7-mediated oncogenic activity independent of RB1 inactivation.\n\nSignificance StatementHuman papillomaviruses uncouple proliferation from differentiation in order to enable virus replication in epithelial cells. HPV E7 proteins are well established to promote proliferation by binding to and inactivating retinoblastoma family proteins and other cell cycle inhibitors. However, mechanisms by which high-risk HPV oncoproteins inhibit differentiation have not been defined. This paper identifies the first mechanism by which high-risk HPV E7 inhibit keratinocyte differentiation. The inhibition of differentiation requires degradation of the cellular protein PTPN14 by high-risk HPV E7 and this degradation is related to the ability of high-risk HPV oncoproteins to immortalize keratinocytes and to cause cancer.

microbiology↗