Structural basis for the enhanced transcriptional control by the human papillomavirus strain-16 E2 protein.

NADRA, A.D., CICERO, D.O., ELISEO, T., DELLAROLE, M. AND PRAT GAY, G. DE

Pinamar, Argentina. Diciembre 3-6, 2005.

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2005

SAIB

STRUCTURAL BASIS FOR THE ENHANCED TRANSCRIPTIONAL CONTROL BY THE HUMAN PAPILLOMAVIRUS STRAIN-16 E2 PROTEIN Alejandro D. Nadra1, Daniel O. Cicero2, Tommaso Eliseo2, Mariano Dellarole1, and Gonzalo de Prat-Gay1 1 Instituto Leloir and CONICET, 2 Department of Chemical Sciences and Technologies, University of Rome ´Tor Vergata´. E-mail: anadra@leloir.org.ar High risk HPV16 is responsible for the largest percent of the cervical cancers linked to human papillomavirus infection and the E2 protein is a key factor for transcriptional regulation of all viral genes. We present the first structure for the DNA binding domain of HPV16 E2 bound to DNA, and in particular, a natural cognate sequence. The structure was obtained by refining the structure of the free protein using NOE and RDC restrains from the complex. The NMR structure reveals that the overall conformation remains virtually unchanged and chemical shift analysis of the protein bound to a shorter duplex uncovered a contact out of the minimal E2 DNA binding sequence, made by lysine 349, located in ß2 loop, packed against the DNA binding helix. This contact was confirmed by titration calorimetry and mutagenesis, with a contribution of 1.0 kcal mol of this interaction to the overall binding energy. HPV16 E2 is known to have the strongest DNA binding affinity, related to a strict positive and negative control, where the latter translates into the repression of the expression of the E6 and E7 oncogenes, responsible for carcinogenesis. The novel features not previously observed in any related structure provide structural and thermodynamic basis for the tight transcriptional control of this high risk strain. Section: Enzymology and Structural Biology