[Frontiers in Bioscience 14, 900-917, January 1, 2009]

Evolutionary and biophysical relationships among the papillomavirus E2 proteins

Dukagjin M. Blakaj1, Narcis Fernandez-Fuentes2, Zigui Chen3, Rashmi Hegde4, Andras Fiser1, Robert D. Burk3,5, Michael Brenowitz1

1Department of Biochemistry, Albert Einstein College of Medicine,1300 Morris Park Avenue, Bronx NY 10461, 2Leeds Institute of Molecular Medicine, Section of Experimental Therapeutics, St. James Hospital, Leeds LS9 7TF, United Kingdom, 3Department of Microbiology and Immunology, Albert Einstein College of Medicine,1300 Morris Park Avenue, Bronx NY 10461, 4Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Department of Pediatrics, University of Cincinnati School of Medicine, 3333 Burnet Avenue, Cincinnati OH 45229, 5Departments of Obstetrics and Gynecology and Women's Health and Epidemiology and Population Health, Albert Einstein College of Medicine,1300 Morris Park Avenue, Bronx NY 10461

TABLE OF CONTENTS

1. Abstract
2. Introduction
2.1. Overview of structure of E2 protein
2.2. Overview of E2 protein DNA binding
3. Conserved residues yield conserved structure and function
3.1. The electrostatic surface of E2D types and variants
3.2. Transactivation domain sequence conservation at the E2-E1 interaction interface
4. Analysis of HPV16 variants
5. Role of E2 protein in malignancy and its interaction with p53
6. E2-DNA affinity and specificity
6.1. Computational analysis of E2 function and DNA binding
6.2. Modulation of E2 protein binding
7. Significance
8. References

1. ABSTRACT

Infection by human papillomavirus (HPV) may result in clinical conditions ranging from benign warts to invasive cancer. The HPV E2 protein represses oncoprotein transcription and is required for viral replication. HPV E2 binds to palindromic DNA sequences of highly conserved four base pair sequences flanking an identical length variable 'spacer'. E2 proteins directly contact the conserved but not the spacer DNA. Variation in naturally occurring spacer sequences results in differential protein affinity that is dependent on their sensitivity to the spacer DNA's unique conformational and/or dynamic properties. This article explores the biophysical character of this core viral protein with the goal of identifying characteristics that associated with risk of virally caused malignancy. The amino acid sequence, 3d structure and electrostatic features of the E2 protein DNA binding domain are highly conserved; specific interactions with DNA binding sites have also been conserved. In contrast, the E2 protein's transactivation domain does not have extensive surfaces of highly conserved residues. Rather, regions of high conservation are localized to small surface patches. Implications to cancer biology are discussed.