title: UV radiation effects on a DNA repair enzyme: conversion of a [4Fe-4S](2+) cluster into a [2Fe-2S] (2+).
abstract: Organisms are often exposed to different types of ionizing radiation that, directly or not, will promote damage to DNA molecules and/or other cellular structures. Because of that, organisms developed a wide range of response mechanisms to deal with these threats. Endonuclease III is one of the enzymes responsible to detect and repair oxidized pyrimidine base lesions. However, the effect of radiation on the structure/function of these enzymes is not clear yet. Here, we demonstrate the effect of UV-C radiation on E. coli endonuclease III through several techniques, namely UV-visible, fluorescence and Mössbauer spectroscopies, as well as SDS-PAGE and electrophoretic mobility shift assay. We demonstrate that irradiation with a UV-C source has dramatic consequences on the absorption, fluorescence, structure and functionality of the protein, affecting its [4Fe-4S] cluster and its DNA-binding ability, which results in its inactivation. An UV-C radiation-induced conversion of the [4Fe-4S](2+) into a [2Fe-2S](2+) was observed for the first time and proven by Mössbauer and UV-visible analysis. This work also shows that the DNA-binding capability of endonuclease III is highly dependent of the nuclearity of the endogenous iron-sulfur cluster. Thus, from our point of view, in a cellular context, these results strengthen the argument that cellular sensitivity to radiation can also be due to loss of radiation-induced damage repair ability.
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.|CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Filipe
authors.initials: F
authors.lastname: Folgosa
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Inês
authors.initials: I
authors.lastname: Camacho
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Daniela
authors.initials: D
authors.lastname: Penas
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Márcia
authors.initials: M
authors.lastname: Guilherme
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Fróis
authors.affiliation: CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Paulo A
authors.initials: PA
authors.lastname: Ribeiro
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Tavares
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal. masp@fct.unl.pt.
authors.forename: Alice S
authors.initials: AS
authors.lastname: Pereira
mesh_terms: D004247:DNA / Q000378:metabolism; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D010957:Plasmids; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D013057:Spectrum Analysis; D014466:Ultraviolet Rays
chemical_list: D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D011994:Recombinant Proteins; D004247:DNA; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli