Towards Understanding of Polymorphism of the G-rich Region of Human Papillomavirus Type 52.

Maja Marušič,Janez Plavec

doi:10.3390/molecules24071294

Abstract

The potential to affect gene expression via G-quadruplex stabilization has been extended to all domains of life, including viruses. Here, we investigate the polymorphism and structures of G-quadruplexes of the human papillomavirus type 52 with UV, CD and NMR spectroscopy and gel electrophoresis. We show that oligonucleotide with five G-tracts folds into several structures and that naturally occurring single nucleotide polymorphisms (SNPs) have profound effects on the structural polymorphism in the context of G-quadruplex forming propensity, conformational heterogeneity and folding stability. With help of SNP analysis, we were able to select one of the predominant forms, formed by G-rich sequence d(G3TAG3CAG4ACACAG3T). This oligonucleotide termed HPV52(1–4) adopts a three G-quartet snap back (3 + 1) type scaffold with four syn guanine residues, two edgewise loops spanning the same groove, a no-residue V loop and a propeller type loop. The first guanine residue is incorporated in the central G-quartet and all four-guanine residues from G4 stretch are included in the three quartet G-quadruplex core. Modification studies identified several structural elements that are important for stabilization of the described G-quadruplex fold. Our results expand set of G-rich targets in viral genomes and address the fundamental questions regarding folding of G-rich sequences.

Highlights

Human papillomaviruses (HPV) are pathogens infecting skin and mucosa that have co-evolved with human species and are well adapted to cause infection with minimal damage to their host
Twenty seven (27) nt long oligonucleotide originating from the genome of HPV type 52 with its five G-rich tracts was expected to adopt a large number of structures, posing a challenge for structural studies
Spectrum of HPV52(1–5) (Figure 1B), which indicated its folding into several G-quadruplex structures

Summary

Introduction

Human papillomaviruses (HPV) are pathogens infecting skin and mucosa that have co-evolved with human species and are well adapted to cause infection with minimal damage to their host. Even though there are currently more than 200 different types of HPVs described [1], only a fraction of those are responsible for the development of diseases in humans. Their life-cycle unravels in synchrony with differentiation of keratinocytes, starting from increased copy number of viral episome in the basal layer, through production of viral protein and assembly of viral particles that are shed from mature keratinocytes when they die [2]. Persistent infection with high-risk HPVs can eventually lead to development of neoplasms and even cancer, most commonly cancer of skin, head and neck and anogenital regions [7,8]. Among most potent high-risk HPVs are HPV16, HPV18, HPV52 and HPV58 with different regional distribution around the world and ability to cause disease [9]

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Conclusion