The HPV E2 Transcriptional Transactivation Protein Stimulates Cellular DNA Polymerase Epsilon

Human papillomavirus associated cervical lesion: pathogenesis and therapeutic interventions

Human papillomavirus (HPV) is the most prevalent sexually transmitted virus globally. Persistent high-risk HPV infection can result in cervical precancerous lesions and cervical cancer, with 70% of cervical cancer cases associated with high-risk types HPV16 and 18. HPV infection imposes a significant financial and psychological burden. Therefore, studying methods to eradicate HPV infection and halt the progression of precancerous lesions remains crucial. This review comprehensively explores the mechanisms underlying HPV-related cervical lesions, including the viral life cycle, immune factors, epithelial cell malignant transformation, and host and environmental contributing factors. Additionally, we provide a comprehensive overview of treatment methods for HPV-related cervical precancerous lesions and cervical cancer. Our focus is on immunotherapy, encompassing HPV therapeutic vaccines, immune checkpoint inhibitors, and advanced adoptive T cell therapy. Furthermore, we summarize the commonly employed drugs and other nonsurgical treatments currently utilized in clinical practice for managing HPV infection and associated cervical lesions. Gene editing technology is currently undergoing clinical research and, although not yet employed officially in clinical treatment of cervical lesions, numerous preclinical studies have substantiated its efficacy. Therefore, it holds promise as a precise treatment strategy for HPV-related cervical lesions.

Phosphorylation of E2 Serine Residue 402 Is Required for the Transcription and Replication of the HPV5 Genome

Cutaneous human papillomavirus type 5 (HPV5) belongs to the supposedly oncogenic β-HPVs associated with specific types of skin and oral cavity cancers. Three viral proteins, namely, helicase E1 and transcription factors E2 and E8^E2, are master regulators of the viral life cycle. HPV5 E2 is a transcriptional activator that also participates in the E1-dependent replication and nuclear retention of the viral genome, whereas E8^E2 counterbalances the activity of E2 and inhibits HPV transcription and replication. In the present study, we demonstrate that the HPV5 E2 protein is extensively phosphorylated by cellular protein kinases, and serine residue 402 (S402) is the highest scoring phosphoacceptor site. This residue is located within a motif conserved among many β-HPVs and in the oncogenic HPV31 α-type. Using the nonphosphorylatable and phosphomimetic mutants, we demonstrate that phosphorylation of the E2 S402 residue is required for the transcription and replication of the HPV5 genome in U2OS cells and human primary keratinocytes. Mechanistically, the E2-S402-phopshodeficient protein is unable to trigger viral gene transcription and has an impaired ability to support E1-dependent replication, but the respective E8^E2-S213 mutant displays no phenotype. However, phosphorylation of the E2 S402 residue has no impact on the E2 stability, subcellular localization, self-assembly, DNA-binding capacity, and affinity to the E1 and BRD4 proteins. Further studies are needed to identify the protein kinase(s) responsible for this phosphorylation. IMPORTANCE Human papillomavirus type 5 (HPV5) may play a role in the development of specific types of cutaneous and head and neck cancers. The persistence of the HPV genome in host cells depends on the activity of its proteins, namely, a helicase E1 and transcription/replication factor E2. The latter also facilitates the attachment of episomal viral genomes to host cell chromosomes. In the present study, we show that the HPV5 E2 protein is extensively phosphorylated by host cell protein kinases, and we identify serine residue 402 as the highest scoring phosphoacceptor site of E2. We demonstrate that the replication of the HPV5 genome may be blocked by a single point mutation that prevents phosphorylation of this serine residue and switches off the transcriptional activity of the E2 protein. The present study contributes to a better understanding of β-HPV5 replication and its regulation by host cell protein kinases.

Senolytic Therapy: A Potential Approach for the Elimination of Oncogene-Induced Senescent HPV-Positive Cells

Senescence represents a unique cellular stress response characterized by a stable growth arrest, macromolecular alterations, and wide spectrum changes in gene expression. Classically, senescence is the end-product of progressive telomeric attrition resulting from the repetitive division of somatic cells. In addition, senescent cells accumulate in premalignant lesions, in part, as a product of oncogene hyperactivation, reflecting one element of the tumor suppressive function of senescence. Oncogenic processes that induce senescence include overexpression/hyperactivation of H-Ras, B-Raf, and cyclin E as well as inactivation of PTEN. Oncogenic viruses, such as Human Papilloma Virus (HPV), have also been shown to induce senescence. High-risk strains of HPV drive the immortalization, and hence transformation, of cervical epithelial cells via several mechanisms, but primarily via deregulation of the cell cycle, and possibly, by facilitating escape from senescence. Despite the wide and successful utilization of HPV vaccines in reducing the incidence of cervical cancer, this measure is not effective in preventing cancer development in individuals already positive for HPV. Accordingly, in this commentary, we focus on the potential contribution of oncogene and HPV-induced senescence (OIS) in cervical cancer. We further consider the potential utility of senolytic agents for the elimination of HPV-harboring senescent cells as a strategy for reducing HPV-driven transformation and the risk of cervical cancer development.

HPV-16 E2/E6 and POU5F1B as Biomarkers to Determine Cervical High-Grade Squamous Lesions and More

Purpose

Human papillomavirus-16 (HPV-16) is the most carcinogenic HPV genotype. This study aimed to evaluate the clinical value of POU5F1B and HPV-16-E2/E6 by cervical cytology specimens to predict the cervical intraepithelial neoplasia two grade and more (CIN2+).

Methods

Finally, 248 patients with HPV-16 single infection were enrolled. Using cytology specimen by real-time quantitative PCR (qPCR), POU5F1B mRNA and HPV-16-E2/E6 were detected. The relationship of POU5F1B, HPV-16-E2/E6 and CIN2+ were analyzed, and the optimal cut-off values of POU5F1B and HPV-16-E2/E6 to predict CIN2+ were calculated.

Results

The mean HPV-16-E2/E6 decreased significantly with cervical lesions development, especially compared with CIN2+ (p<0.05). And the POU5F1B demonstrated higher expression in CIN2+ than that of normal cervical tissue and CIN1 (p<0.05). What is more, POU5F1B was negatively correlated with HPV-16-E2/E6. It demonstrated that the area under the receiver operating characteristic curve (AUC) for POU5F1B (0.9058) was higher than that for HPV-16-E2/E6 (0.8983), and the sensitivity and specificity of POU5F1B in the diagnosis of CIN2+ were higher than HPV-E2/E6. Furthermore, it demonstrated that the POU5F1B had the highest odds ratio (OR= 16.84; 95% CI (8.00–35.46)) for the detection of CIN 2+.

Conclusion

HPV-16-E2/E6≤0.6471 or POU5F1B≥1.0310 in cervical exfoliated cells can be used as a reliable predictor of CIN2+. POU5F1B can be used as a new auxiliary biomarker to determine the HPV infection status and a reliable predictor of CIN2+. The expression of POU5F1B≥1.0310 had the highest OR for the detection of CIN2+.