Virus-host protein-protein interactions between human papillomavirus 16 E6 A1 and D2/D3 sub-lineages: variances and similarities

Abstract

High-risk strains of human papillomavirus are causative agents for cervical and other mucosal cancers with type 16 being the most frequent. Compared to the European Prototype (A1 denoted “EP”), the Asian-American (D2/D3 denoted “AA”) sub-lineage or “variant” was reported to have increased abilities to promote carcinogenesis. Few, if any global interactome studies, have looked at protein-protein interactions (PPIs) between host proteins and variants of the key transforming E6 protein. We applied a primary human foreskin keratinocyte model transduced with EP and AA variant E6 genes and co-immunoprecipitated expressed E6 proteins along with interacting cellular proteins to potentially detect diversity in virus-host relationships. We reasoned that due to single nucleotide polymorphisms, AAE6 and EPE6 may have unique PPIs with host cellular proteins—conferring gain or loss of function—resulting in varied abilities to promote carcinogenesis. Using liquid chromatography-mass spectrometry and stringent interactor selection based on the number of peptides, we identified 25 candidates: 6 unique to AAE6 and EPE6, respectively along with 13 common E6 targets between AAE6 and EPE6. We also applied a more inclusive process based on pathway selection and discovered 171 target proteins: 90 unique AAE6 and 61 unique EPE6 along with 20 common E6 targets between the two sub-lineages. Interpretations for both approaches were made drawing from different databases such as UniProt, BioGRID and Reactome. The detected E6 targets were found to be implicated in deregulating a variety of cellular functions such as DNA replication and repair, energetics and hypoxia, mitogen-activated protein kinases/extracellular signal-regulated kinases signaling, tumour suppression and immune response, as well as pathways hijacked from embryogenesis and wound healing to drive cancer development. Validation experiments such as reverse co-immunoprecipitation and RNA interference are required to substantiate these findings. Here, we provide an unprecedented resource for new research questions and hypotheses testing in HR HPV biology. If variant-specific interactions are verified, their targeted disruption may potentially yield new options for personalized cancer treatment strategies.