KRAS Promoter G-Quadruplexes from Sequences of Different Length: A Physicochemical Study.

Federica D’Aria,Luigi Petraccone,Bruno Pagano,Concetta Giancola

doi:10.3390/ijms22010448

Federica D’Aria, Luigi Petraccone + Show 2 more

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https://doi.org/10.3390/ijms22010448

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Abstract

DNA G-quadruplexes (G4s) form in relevant genomic regions and intervene in several biological processes, including the modulation of oncogenes expression, and are potential anticancer drug targets. The human KRAS proto-oncogene promoter region contains guanine-rich sequences able to fold into G4 structures. Here, by using circular dichroism and differential scanning calorimetry as complementary physicochemical methodologies, we compared the thermodynamic stability of the G4s formed by a shorter and a longer version of the KRAS promoter sequence, namely 5′-AGGGCGGTGTGGGAATAGGGAA-3′ (KRAS 22RT) and 5′-AGGGCGGTGTGGGAAGAGGGAAGAGGGGGAGG-3′ (KRAS 32R). Our results show that the unfolding mechanism of KRAS 32R is more complex than that of KRAS 22RT. The different thermodynamic stability is discussed based on the recently determined NMR structures. The binding properties of TMPyP4 and BRACO-19, two well-known G4-targeting anticancer compounds, to the KRAS G4s were also investigated. The present physicochemical study aims to help in choosing the best G4 target for potential anticancer drugs.

Highlights

The discovery of G-quadruplex (G4) arrangements in G-rich DNA sequences has shed light on possible new biological functions for DNA
G4s were found in oncogene promoter regions that are crucial for the development of cancer [7]
The authors found folding enthalpy obtained by circular dichroism (CD) measurements is model-dependent, being calculated by that Kirsten ras (KRAS) 32R folds into two main parallel conformations in equilibrium with each other

Summary

Introduction

The discovery of G-quadruplex (G4) arrangements in G-rich DNA sequences has shed light on possible new biological functions for DNA. G4s are nucleic acid structures formed in relevant genomic regions, such as telomeres and oncogene promoters [1]. A growing body of evidence supports the notion that G4s formed by promoter sequences are involved in the regulation of gene expression [5,6]. G4s were found in oncogene promoter regions that are crucial for the development of cancer [7]. For these reasons, targeting G4s in gene promoter regions can result into a very effective anticancer approach whose huge potential is still to be explored [8,9]. Many gene promoter G4s have biophysical and structural properties that make them good targets for drug design, and their structural diversity suggests that a high degree of selectivity might be possible

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