Role of XRCC1 in the Coordination and Stimulation of Oxidative DNA Damage Repair Initiated by the DNA Glycosylase hOGG1

Abstract

XRCC1 participates in DNA single strand break and base excision repair (BER) to preserve genetic stability in mammalian cells. XRCC1 participation in these pathways is mediated by its interactions with several of the acting enzymes. Here, we report that XRCC1 interacts physically and functionally with hOGG1, the human DNA glycosylase that initiates the repair by BER of the mutagenic oxidized base 8-oxoguanine. This interaction leads to a 2-to 3-fold stimulation of the DNA glycosylase activity of hOGG1. XRCC1 stimulates the formation of the hOGG1 Schiff-base DNA intermediate without interfering with the endonuclease activity of APE1, the second enzyme in the pathway. On the contrary, the stimulation in the appearance of the incision product seems to reflect the addition of the effects of XRCC1 on the two first enzymes of the pathway. The data presented support a model by which XRCC1 will pass on the DNA intermediate from hOGG1 to the endonuclease APE1. This results in an acceleration of the overall repair process of oxidized purines to yield an APE1-cleaved abasic site, which can be used as a substrate by DNA polymerase ␤. More importantly, the results unveil a highly coordinated mechanism by which XRCC1, through its multiple protein-protein interactions, extends its orchestrating role from the base excision step to the resealing of the repaired DNA strand.A major threat to genetic stability is the damaging of DNA by either endogenous or exogenous compounds. This is underscored by the cancer-prone phenotype of human cells defective in DNA repair processes. Exposure of the cellular DNA to reactive oxygen species (ROS), 1 generated either by the normal metabolism of the cell or by chemical and physical exogenous agents, is at the origin of lesions that can have genotoxic or mutagenic consequences. To avoid the effects of ROS and, therefore, to maintain the integrity of their genetic information, organisms have evolved multiple DNA repair mechanisms (1). Because of its capacity to pair with an adenine during replication, 7,8-dihydro-8-oxoguanine (8-oxoG), an oxidized derivative of guanine, is arguably the major mutagenic lesion in DNA. Indeed, in Escherichia coli, the inactivation of the genes involved in the repair of this oxidized base leads to one of the strongest spontaneous mutator phenotypes, characterized by the exclusive increase in G to T transversions. Like for other ROS-induced modifications of DNA, 8-oxoG is mainly repaired by the base excision repair (BER) pathway. This pathway is initiated by the recognition and excision of the oxidized guanine by a DNA glycosylase, OGG1 being the major one in yeast and mammalian cells (2). In human cells, the resulting abasic (apurinic/apyrimidinic (AP)) site can be cleaved by a second enzymatic activity of the hOGG1 polypeptide, namely an AP lyase activity. If such a reaction takes place, the nick produced has a 3Ј-open aldehyde residue that is supposed to be removed by the 3Ј-deoxyribose phosphatase activity of APE1, the major AP endonuclease. However, recent data s...

A unified view of base excision repair: Lesion-dependent protein complexes regulated by post-translational modification

“…This reduction of the 3'lyase activity of bi-functional glycosylases is further supported by the interaction of OGG1 with XRCC1 [34]. OGG1 interacts physically and functionally with XRCC1 to stimulate base hydrolysis without inhibiting the subsequent APE1 strand incision step, resulting in an overall increase in processing of toxic intermediates through the pathway and highlighting the orchestrating abilities of XRCC1 [34]. Nevertheless, should the 3'unsaturated aldehyde present as a repair blocking lesion, APE1 3'phosphodiesterase activity has the ability to remove it to restore active repair [30].…”

“…Furthermore, each of these proteins is reported to interact with XRCC1/ LigIIIα [34,60,61,90], (and in some cases PARP1) supporting the idea that XRCC1/LigIIIα, together with PARP1, acts as a scaffold to coordinate a broad range of substrates and proteins through the BER pathway.…”

“…Similarly, OGG1and MYH showed an enhancement of glycosylase activity and suppression of the glycosylase 3' lyase function upon addition of APE1, suggesting that circumventing the 3'lyase activity is commonly observed for bi-functional glycosylases in vivo [31][32][33]. This reduction of the 3'lyase activity of bi-functional glycosylases is further supported by the interaction of OGG1 with XRCC1 [34]. OGG1 interacts physically and functionally with XRCC1 to stimulate base hydrolysis without inhibiting the subsequent APE1 strand incision step, resulting in an overall increase in processing of toxic intermediates through the pathway and highlighting the orchestrating abilities of XRCC1 [34].…”

“…In the past several years, XRCC1 coordination was further expanded to include pathway initiation enzymes (e.g. ; MPG, OGG1 and NEIL2) as well as APE1, firmly establishing XRCC1 in the orchestration of the entire BER pathway [23,28,34,40]. Thus, XRCC1 interacts with most, if not all components of the BER short-patch pathway.…”

“…The BER mechanism can be viewed as a multitude of protein complexes unique to the initiating lesion (Table I), with XRCC1 (in concert with its binding partner LigIIIα) acting as a scaffold to orchestrate the movement of DNA repair intermediates from repair initiation and strand scission (DNA glycosylase and APE1) to gap tailoring (APE1 and/or pol ß) and facilitating repair completion (LigIIIα) through a series of protein interactions [34,111,112]. For example, an interaction between XRCC1 and PNKP, a protein necessary for the initial processing of DNA single-strand break termini into ends that are amenable to re-ligation, was shown to be involved in BER following oxidative stress [58,63].…”