IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
Cytosolic accumulation of HPV16 E7 oligomers supports different transformation routes for the prototypic viral oncoprotein: The amyloid-cancer connection
Autor/es:
SMAL, C.; WETZLER, D.E.; DANTUR, K.I.; CHEMES, L.; GARCIA ALAI, M.M.; DELLAROLE, M.; ALONSO, L.G.; GASTON, K.; PRAT GAY G. DE
Revista:
BIOCHEMISTRY
Editorial:
AMER CHEMICAL SOC
Referencias:
Año: 2009 vol. 48 p. 11939 - 11949
ISSN:
0006-2960
Resumen:
Transcription of the human papillomavirus E7 oncoprotein is negatively
controlled by the viral E2 protein, and loss of this repression leads to
irreversible transformation and carcinogenesis. Here we show that
interaction of the HPV16 E7 protein with the DNA binding domain of the
E2 protein (E2C) leads to ionic strength-dependent
hetero-oligomerization even at the lowest concentrations measurable.
Titration experiments followed by light scattering and native gel
electrophoresis show insoluble oligomeric complexes with a >or=2000
nm diameter and intermediate soluble complexes 40 and 115 nm in
diameter, respectively, formed in excess of E2C. A discrete oligomeric
soluble complex formed in excess of E7 displays a diameter of 12 nm. The
N-terminal domain of E7 interacts with E2C with a K(D) of 0.1 muM,
where the stretch of residues 25-40 of E7, encompassing both a PEST
motif and phosphorylation sites, is sufficient for the interaction.
Displacement of the soluble E7-E2C complex by an E2 site DNA duplex and
site-directed mutagenesis indicate that the protein-protein interface
involves the DNA binding helix of E2. The formation of complexes of
different sizes and properties in excess of either of the viral proteins
reveals a finely tuned mechanism that could regulate the intracellular
levels of both proteins as infection and transformation progress.
Sequestering E2 into E7-E2 oligomers provides a possible additional
route to uncontrolled E7 expression, in addition and prior to the
disruption of the E2 gene during viral integration into the host genome.