Complementary Functions of Plant AP Endonucleases and AP Lyases during DNA Repair of Abasic Sites Arising from C:G Base Pairs.

Marina Jordano-Raya,Rafael R Ariza,M Isabel Martínez-Macías,Teresa Roldán-Arjona,Dolores Córdoba-Cañero,M Dolores Moreno-Recio,Cristina Beltrán-Melero

doi:10.3390/ijms22168763

Abstract

Abasic (apurinic/apyrimidinic, AP) sites are ubiquitous DNA lesions arising from spontaneous base loss and excision of damaged bases. They may be processed either by AP endonucleases or AP lyases, but the relative roles of these two classes of enzymes are not well understood. We hypothesized that endonucleases and lyases may be differentially influenced by the sequence surrounding the AP site and/or the identity of the orphan base. To test this idea, we analysed the activity of plant and human AP endonucleases and AP lyases on DNA substrates containing an abasic site opposite either G or C in different sequence contexts. AP sites opposite G are common intermediates during the repair of deaminated cytosines, whereas AP sites opposite C frequently arise from oxidized guanines. We found that the major Arabidopsis AP endonuclease (ARP) exhibited a higher efficiency on AP sites opposite G. In contrast, the main plant AP lyase (FPG) showed a greater preference for AP sites opposite C. The major human AP endonuclease (APE1) preferred G as the orphan base, but only in some sequence contexts. We propose that plant AP endonucleases and AP lyases play complementary DNA repair functions on abasic sites arising at C:G pairs, neutralizing the potential mutagenic consequences of C deamination and G oxidation, respectively.

Highlights

Abasic sites are inescapable DNA lesions arising by spontaneous hydrolysis of the N-glycosylic bond between intact nucleobases and deoxyribose [1]
It has been recently reported that the phosphodiesterase activity of human APE1 plays a relevant role in processing 30 -PUA ends generated by the lyase activity of NTHL1 in nucleosomal, but not in naked, DNA [24]
We recently reported that FPG, the major AP lyase of Arabidopsis thaliana, has a relevant biological role in the repair of AP sites generated by the spontaneous release of

Summary

Introduction

Abasic (apurinic/apyrimidinic, AP) sites are inescapable DNA lesions arising by spontaneous hydrolysis of the N-glycosylic bond between intact nucleobases and deoxyribose [1]. Results in weakening of the N-glycosylic bond and a marked increase in base loss [2,3,4]. AP sites exist as an equilibrium mixture of hemiacetals of the closed furanose form, but approximately 1% is present as the ring-opened aldehyde species which is prone to spontaneous hydrolysis and may generate single-strand breaks (SSBs) [10,11]. Unrepaired AP sites are cytotoxic since they block DNA replication and transcription. DNA replication blockage may be avoided through translesion DNA synthesis across the AP site, which usually results in mutations [12,13]

Methods

Results

Conclusion