Mus308 Processes Oxygen and Nitrogen Ethylation DNA Damage in Germ Cells of Drosophila

Abstract

The D. melanogaster mus308 gene, highly conserved among higher eukaryotes, is implicated in the repair of cross-links and of O-ethylpyrimidine DNA damage, working in a DNA damage tolerance mechanism. However, despite its relevance, its possible role on the processing of different DNA ethylation damages is not clear. To obtain data on mutation frequency and on mutation spectra in mus308 deficient (mus308−) conditions, the ethylating agent diethyl sulfate (DES) was analysed in postmeiotic male germ cells. These data were compared with those corresponding to mus308 efficient conditions. Our results indicate that Mus308 is necessary for the processing of oxygen and N-ethylation damage, for the survival of fertilized eggs depending on the level of induced DNA damage, and for an influence of the DNA damage neighbouring sequence. These results support the role of mus308 in a tolerance mechanism linked to a translesion synthesis pathway and also to the alternative end-joinig system.

The Comet Assay in Drosophila: A Tool to Study Interactions between DNA Repair Systems in DNA Damage Responses In Vivo and Ex Vivo

“…When this protein is not working, DNA strand breaks could be formed from MMS-induced DNA damage if this damage were not bypassed, and, moreover, once formed, the breaks would not be re-joined. To our knowledge, this is the first time that this effect has been detected in somatic cells, and it agrees with that detected in Drosophila germ cells in vivo [36].…”

“…A higher sensitivity to the toxic effects of MMS was expected for the mus201 strain [41] and, therefore, also for the double mutant mus201;mus308 one; a higher sensitivity to nitrogen alkylation DNA damage could also be expected for the mus308 strain, at least when the levels of DNA damage are high [36].…”

“…Because of this, only the MMS effect should be compared among strains; clearly, this chemically induced DNA strand breaks in all the strains in a linear relationship with the dose in all of them, but in the double mutant one, as shown in Figure 1, where the averaged MMS-induced TM values obtained for each analyzed strain are presented. MMS was chosen as a genotoxic agent because it induces mostly nitrogen alkylations [30], some of which can indirectly induce DNA strand breaks through the generation of abasic (AP) sites [31], and because nitrogen alkylations are repaired in Drosophila mainly by the NER system [40], since no methylpurine DNA glycosylase has ever been found [43]; moreover, the dmPolQ protein seems to play a role in the processing of nitrogen ethylations in germ cells, especially when NER is saturated by high levels of DNA damage [36]. Therefore, these results fit with the known mechanism of action for this chemical.…”

“…Oregon K (OK), a wild-type strain efficient for all the repair systems, -mus201, homozygous for the mus201 D1 mutant allele of the dmXPG gene [28,32] and, therefore, deficient for the NER repair system -mus308, homozygous for the mus308 D2 mutant allele of the gene encoding the dmPolQ protein [29], a homologue of the human DNA polymerase Q [33]. It is deficient in the repair of DNA cross-links and persistent oxygen alkylation DNA damage [34,35], and possibly also in the repair of nitrogen alkylation [36], working both in an alternative end-joining process called microhomology-mediated end joining (MMEJ) and in the damage bypass [37,38]. -mus201;mus308, a homozygous double mutant for the mus201 D1 and mus308 D2 alleles, was obtained in our laboratory by crossing the individual mutant strains using balancer stocks.…”

Interaction between gene repair and mobile elements-induced activity systems after low-dose irradiation

“…is defected in the gene mus304 (allele D1) which takes in post-replication DNA repair and recombination, in the repair DSB and excision repair of pyrimidine dimers (Harris and Boyd 1993;Brodsky et al 2000;Chmuzh et al 2007), homolog of mammal ATRIP gene (Oikemus et al 2006 (Chan et al 2010;D ıaz-Vald es et al 2010), homolog of mammal and human Polq gene (Sharief et al 1999;Shima et al 2004); stock mus309 (genotype: mus309[D3,ry]/CyO) (allele D3) has violation of the system repair DSB (Beall and Rio 1997;Portin 2010), homolog of mammal Kup70 and human XRCC6 genes (Beall and Rio 1996;Pei et al 2013).…”