| Abstrakt: |
Given the fundamental role of MRE11 in many aspects of DNA metabolism and signalling in eukaryotes, we analysed the impact of several MRE11 mutations on DNA damage response ( DDR) and DNA repair in Arabidopsis thaliana. Three different atmre11 and an atatm-2 mutant lines, together with the wild type ( WT), were compared using a new Arabidopsis genotoxic assay for in situ evaluation of genome integrity and DNA damage repair efficiency after double strand break ( DSB) induction. The results showed that, despite the phenotypic differences and different lengths of the putative truncated At MRE11 proteins, all three atmre11 and the atatm-2 mutant lines exhibited common hypersensitivity to bleomycin treatment, where they only slightly reduced mitotic activity, indicating a G2/M checkpoint abrogation. In contrast to the WT, which reduced the frequency of chromosomal aberrations throughout the recovery period after treatment, none of the three atmre11 and atatm-2 mutants recovered. Moreover, atmre11-3 mutants, similarly to atatm-2 mutants, failed to transcriptionally induce several DDR genes and had altered expression of the CYCB1;1:: GUS protein. Nevertheless, numerous chromosomal fusions in the atmre11 mutants, observed after DNA damage induction, suggest intensive DNA repair activity. These results indicate that functional and full-length At MRE11 is essential for activation of the cell cycle arrest, transcriptional regulation and DNA repair upon induction of DSB. [ABSTRACT FROM AUTHOR] |
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