title: Ribonucleotide reductase regulation in response to genotoxic stress in Arabidopsis.
abstract: Ribonucleotide reductase (RNR) is an essential enzyme that provides dNTPs for DNA replication and repair. Arabidopsis (Arabidopsis thaliana) encodes three AtRNR2-like catalytic subunit genes (AtTSO2, AtRNR2A, and AtRNR2B). However, it is currently unclear what role, if any, each gene contributes to the DNA damage response, and in particular how each gene is transcriptionally regulated in response to replication blocks and DNA damage. To address this, we investigated transcriptional changes of 17-d-old Arabidopsis plants (which are enriched in S-phase cells over younger seedlings) in response to the replication-blocking agent hydroxyurea (HU) and to the DNA double-strand break inducer bleomycin (BLM). Here we show that AtRNR2A and AtRNR2B are specifically induced by HU but not by BLM. Early AtRNR2A induction is decreased in an atr mutant, and this induction is likely required for the replicative stress checkpoint since rnr2a mutants are hypersensitive to HU, whereas AtRNR2B induction is abolished in the rad9-rad17 double mutant. In contrast, AtTSO2 transcription is only activated in response to double-strand breaks (BLM), and this activation is dependent upon AtE2Fa. Both TSO2 and E2Fa are likely required for the DNA damage response since tso2 and e2fa mutants are hypersensitive to BLM. Interestingly, TSO2 gene expression is increased in atr versus wild type, possibly due to higher ATM expression in atr. On the other hand, a transient ATR-dependent H4 up-regulation was observed in wild type in response to HU and BLM, perhaps linked to a transient S-phase arrest. Our results therefore suggest that individual RNR2-like catalytic subunit genes participate in unique aspects of the cellular response to DNA damage in Arabidopsis.
authors: Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg cedex, France.
authors: Hélène
authors: H
authors: Roa
authors: Julien
authors: J
authors: Lang
authors: Kevin M
authors: KM
authors: Culligan
authors: Murielle
authors: M
authors: Keller
authors: Sarah
authors: S
authors: Holec
authors: Valérie
authors: V
authors: Cognat
authors: Marie-Hélène
authors: MH
authors: Montané
authors: Guy
authors: G
authors: Houlné
authors: Marie-Edith
authors: ME
authors: Chabouté
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D005075:Biological Evolution; D004249:DNA Damage / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D010641:Phenotype; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D012264:Ribonucleotide Reductases; C512168:TSO2 protein, Arabidopsis; C512169:ribonucleotide reductase 2A, Arabidopsis; C512170:ribonucleotide reductase 2B, Arabidopsis