The Role of Protein Kinase A Regulation of the E6 PDZ-Binding Domain during the Differentiation-Dependent Life Cycle of Human Papillomavirus Type 18

Abstract

Human papillomavirus (HPV) E6 proteins of high-risk alpha types target a select group of PSD95/DLG1/ZO1 (PDZ) domain-containing proteins by using a C-terminal PDZ-binding motif (PBM), an interaction that can be negatively regulated by phosphorylation of the E6 PBM by protein kinase A (PKA). Here, we have mutated the canonical PKA recognition motif that partially overlaps with the E6 PBM in the HPV18 genome (E6153PKA) and compared the effect of this mutation on the HPVl8 life cycle in primary keratinocytes with the wild-type genome and with a second mutant genome that lacks the E6 PBM (E6ΔPDZ). Loss of PKA recognition of E6 was associated with increased growth of the genome-containing cells relative to cells carrying the wild-type genome, and upon stratification, a more hyperplastic phenotype, with an increase in the number of S-phase competent cells in the upper suprabasal layers, while the opposite was seen with the E6ΔPDZ genome. Moreover, the growth of wild-type genome-containing cells was sensitive to changes in PKA activity, and these changes were associated with increased phosphorylation of the E6 PBM. In marked contrast to E6ΔPDZ genomes, the E6153PKA mutation exhibited no deleterious effects on viral genome amplification or expression of late proteins. Our data suggest that the E6 PBM function is differentially regulated by phosphorylation in the HPV18 life cycle. We speculate that perturbation of protein kinase signaling pathways could lead to changes in E6 PBM function, which in turn could have a bearing on tumor promotion and progression.

Papillomavirus E6 PDZ Interactions Can Be Replaced by Repression of p53 To Promote Episomal Human Papillomavirus Genome Maintenance

“…It is unclear from our experiments whether HPV-16_E6⌬PBM genomes are lost immediately or progressively during cell passaging, but this has been addressed in a recent publication from the Roberts laboratory, which demonstrated that HPV-18 genomes where PBM is deleted from E6 are maintained episomally in early passage transfected keratinocytes, but progressively lost upon cell passaging (37). It is also possible that there could be differences in outcome had our experiments been conducted in primary keratinocytes instead of NIKS cells, where HPV oncogene expression is not necessary for NIKS immortalization.…”

E6/E7 proteins are potential markers for the screening and diagnosis of cervical pre‑cancerous lesions and cervical cancer in a Chinese population

“…HR HPV, which is considered to be a necessary biological factor for CC, can express specific viral genes such as E6 and E7, which have been observed in CC cell lines and biopsies (4,5). These specific viral genes express oncoproteins (such as E6 and E7 proteins) that can be inserted into the host's cell genome (6).…”

PDZRN3/LNX3 Is a Novel Target of Human Papillomavirus Type 16 (HPV-16) and HPV-18 E6

“…The E6 oncoproteins of high-risk HPV types have a C-terminal PDZ-binding motif (PBM) that is important for a normal viral life cycle and progeny production (for a review, see reference 3). PBM deletion causes viral genome integration, loss of replicative competence, and an increased potential for oncogenic transformation (4)(5)(6)(7)(8).…”