title: Insights into the mechanism of human papillomavirus E2-induced procaspase-8 activation and cell death.
abstract: High-risk human papillomavirus (HR-HPV) E2 protein, the master regulator of viral life cycle, induces apoptosis of host cell that is independent of its virus-associated regulatory functions. E2 protein of HR-HPV18 has been found to be involved in novel FADD-independent activation of caspase-8, however, the molecular basis of this unique non-death-fold E2-mediated apoptosis is poorly understood. Here, with an interdisciplinary approach that involves in silico, mutational, biochemical and biophysical probes, we dissected and characterized the E2-procasapse-8 binding interface. Our data demonstrate direct non-homotypic interaction of HPV18 E2 transactivation domain (TAD) with α2/α5 helices of procaspase-8 death effector domain-B (DED-B). The observed interaction mimics the homotypic DED-DED complexes, wherein the conserved hydrophobic motif of procaspase-8 DED-B (F122/L123) occupies a groove between α2/α3 helices of E2 TAD. This interaction possibly drives DED oligomerization leading to caspase-8 activation and subsequent cell death. Furthermore, our data establish a model for E2-induced apoptosis in HR-HPV types and provide important clues for designing E2 analogs that might modulate procaspase-8 activation and hence apoptosis.
authors.affiliation: Integrated Biophysics and Structural Biology (IBSB) Laboratory, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Navi Mumbai, India.
authors.forename: Nitu
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Biotechnology, Office No. 503, Lab No. 510, Indian Institute of Technology Madras, Adyar, Chennai, 600036, India.
authors.forename: Sanjib
authors.initials: S
authors.lastname: Senapati
authors.affiliation: Integrated Biophysics and Structural Biology (IBSB) Laboratory, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Navi Mumbai, India.
authors.forename: Kakoli
authors.initials: K
authors.lastname: Bose
mesh_terms: D017209:Apoptosis; D001665:Binding Sites; D053181:Caspase 8 / Q000737:chemistry / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009856:Oncogene Proteins, Viral / Q000737:chemistry / Q000502:physiology*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport
chemical_list: D004792:Enzyme Precursors; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D009856:Oncogene Proteins, Viral; C069102:oncogene protein E2, Human papillomavirus type 18; C505530:CASP8 protein, human; D053181:Caspase 8