relationships at low dose IR Dik C. van Gent, Erasmus MC Modeling - PowerPoint PPT Presentation

Linear and non-linear dose-effect relationships at low dose IR Dik C. van Gent, Erasmus MC

Modeling of the dose-response curve LNT, threshold, hypersensitive, hormesis? What can we measure at low dose? - DNA repair (linear 10-1000 mGy) - micronuclei (linear) - chromosomal translocation (linear) What about uptake extrachromosomal DNA? What about transcriptional responses?

Random integration assay

137 Cs ☢ 75% attenuator

Repair mutants behave like wt

H2AX is required for stimulation

H2AX is required for stimulation WT Ubi mutants Phospho mutants

Plateau in dose-response relative integration ~0.2 Gy ~0.5-1 Gy ~5-10x Induction of v alternative EJ? ~2x 0.005 Gy IR dose

Regulation of the DNA damage response IR DNA double strand breaks Oxidative damage? Gene expression changes Apoptosis or senescence Cell cycle checkpoints Growth status Aging/age related diseases

Double-strand break repair pathways end processing RAD54 DNA-PK Homologous Recombination DNA end-joining (NHEJ)

Low dose gene expression profiles 0 Gy 0.2 Gy Mice irradiated 0.2 Gy, 0.2 Gy/hr 2 hours later, liver isolated mRNA isolation Micro array analysis Significant genes

DSB induced genes Known Responsive genes: • Gadd45a/b Fold induction IR responsive gene • P21 (CDKN1A) Untreated • Sesn2 0.2 Gy IR • cycB (Ccnb1) • Puma (Bbc3) • Atf3 • DDB2 • MDM2 • BAG3 • SLUG (Snai2) Rad54/ WT Rad54 DNA-PK DNA-PK

Tp53 regulation ATM P21 etc phosphorylation p53 MDM2 degradation WT transcription dephosphorylation stimulation Cyclin G1 PP2A All genes that downregulate p53 are upregulated! WT Rad5 4

Regulation of gene expression after IR IR Other damage DNA double strand breaks NF κ B pathway Acute phase response ERK signaling p53 Lipid metabolism More, e.g. splicing?

No luciferase unirradiated Wt RAD54 DNA-PK P21 reporter mice double No luciferase 0.2 Gy, 4 hours Wt RAD54 DNA-PK double No luciferase 0.2 Gy, 24 hours Wt RAD54 DNA-PK double

Alex Zelensky Mascha Schoonakkers Jeroen Essers Paula van Heijningen Ricardo Leite Yanto Ridwan Stefan Sigurdsson Roland Kanaar Jan Hoeijmakers Colin Henderson Dik van Gent Dept. of Genetics Roland Wolf Div. of Cancer Res., univ. Of Dundee, UK Sigrid Swagemakers Bioinformatics Center Marjolein Sutmuller Sylwia Kabacik René Huiskamp Christophe Badie Department of Radiation & Environment Health Protection Agency, Didcot, UK Petten, Netherlands