Fig. 6.

Haploinsufficiency in Chk1 predisposes to DNA damage in response to MYC overexpression. a B220⁺ IgM⁻ pro/pre B cells FACS sorted from the bone marrow (left) or total splenocytes of mice of the indicated genotypes were processed immediately for immunoblotting using the indicated antibodies. * Indicates that the same CHK1 western is also shown in Fig. 5a, bottom right, lanes 7–12. Membranes were reprobed for PARP1 and γH2A.X here b FACS sorted bone marrow B220⁺ IgM⁻ pro/pre B cells were fixed in ethanol and then processed for intracellular γH2A.X staining. Bars represent means of n = 4–5 (Eµ-MYC ⁺/Eµ-MYC ⁺ Chk1 ^+/−) animals ± S.E.M. c, d γH2A.X staining of pre B cell lines generated from the bone marrow of 2-weeks-old VavBCL2 ⁺ Eμ-MYC ⁺ Chk1 ^+/+ or VavBCL2 ⁺ Eμ-MYC ⁺ Chk1 ^+/− mice. c Steady state γH2A.X -levels d γH2A.X -levels of VavBCL2 ⁺ Eμ-MYC ⁺ cells treated with 500 nM PF-477736 (CHK1i) or solvent control (DMSO) for 24 h (n = 3). Bars in c and d represent means of n = 3/genotype or treatment ± S.E.M. *p < 0.05, **p < 0.01, ***p < 0.001 using unpaired Student´s t test. Abbreviations: fl. full length, cl. cleaved fragment of PARP1