Grants and Contributions:

Title:

Role of C. elegans AP endonuclease, APN-1, in removing DNA lesions generated through transporter-mediated uptake of naturally occurring toxic compounds.

Agreement Number:

RGPIN

Agreement Value:

$170,000.00

Agreement Date:

May 10, 2017 -

Organization:

Natural Sciences and Engineering Research Council of Canada

Location:

Quebec, CA

Reference Number:

GC-2017-Q1-01854

Agreement Type:

Grant

Report Type:

Grants and Contributions

Additional Information:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

Recipient's Legal Name:

Ramotar, Dindial (Université de Montréal)

Program:

Discovery Grants Program - Individual

Program Purpose:

Damage to the DNA can occur naturally by endogenous agents such as reactive oxygen species, and by several exogenous agents such as polycyclic aromatic compounds and oxidized metabolites. These agents can create hundreds of distinct DNA lesions including oxidative base damage that can undergo further structural changes to give rise to even more toxic DNA lesions. If these DNA lesions are not repaired, they can alter the genome to cause cell death and thus lead to many age related diseases. To avoid these deleterious effects, there are several pathways that act to remove specific classes of DNA lesions. Since 1993, we have been focusing on the base-excision DNA repair pathway that acts to remove oxidative DNA lesions. This pathway is made up of several enzymatic steps involving the recognition of the oxidative DNA lesions, removing the lesions, and restoring the DNA sequence to normal; our focus was mostly on the second step. In this step, following removal of the damage base by DNA glycosylase, the resulting apurinic/apyrimidinic (AP) site is cleaved by an AP endonuclease to initiate DNA repair synthesis. There are two distinct families of AP endonucleases, exemplified by Escherichia coli endonuclease IV (Endo IV/APN-1) and exonuclease III (Exo-3). Both family members are conserved in the yeast Saccharomyces cerevisiae as well as in the worm Caenorhabditis elegans . In C. elegans , we have identified and isolated the genes encoding the AP endonucleases, APN-1 and EXO-3. We subsequently purified and functionally characterized both APN-1 and EXO-3. These studies revealed some interesting enzymatic functions of APN-1 that are distinct from EXO-3. While APN-1 possesses four enzymatic activities to remove DNA lesions, EXO-3 has only two of the activities. Therefore, we believe APN-1 is far more important than EXO-3 to remove a wide range of DNA lesions in C. elegans . Previously, we reported that in the absence of APN-1 the animals exhibited a high frequency of mutations, suggesting that APN-1 is required to repair damaged DNA to prevent genetic instability. So what is the source of the DNA lesions? In a separate study, we recently discovered that C. elegans has an uptake transporter OCT-2, which can allow the entry of pharmaceutical drugs as well as toxic environmental compounds such as pro-oxidants into the animals. We further showed that oct-2 gene expression is controlled by another transporter OCT-1. In the absence of OCT-1, oct-2 gene expression is stimulated. More strikingly, we found that OCT-2 upregulation shortened the lifespan and increased germ cell death of the animals. We hypothesize that OCT-2 mediates the uptake from the growth environment genotoxic compounds that damage the DNA, and these resulting DNA lesions are repaired by APN-1. Our program, therefore, will provide novel insights how active uptake transporters can induce genetic instability in cells compromised for DNA repair.