Research Paper Volume 6, Issue 1 pp 70—81

Serines 440 and 467 in the Werner syndrome protein are phosphorylated by DNA-PK and affects its dynamics in response to DNA double strand breaks

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Figure 6. Cells overexpressing the phosphorylation mutants are moderately sensitive to etoposide.

(A) Comet assay with AG11395 cells overexpressing either EGFP-WRN wild type (WT) or mutant (S440A, S467A or S440A/S467A) 24 h after 35 μM etoposide treatment. Representive images are shown. (B) Tail length in (A) are indicated. At least 17 cells were measured. Asterisks (*) indicate significant difference between 0 h and 24 h (p<0.05). Plus (+) indicate significant difference between Wild type and mutants. (C) AG11395 cells overexpressing either EGFP-WRN wild type (WT), S440A, S467A or S440A/S467A were treated with 0, 15, 25 or 35 μM etoposide. 24 h after the treatment, cell proliferation was evaluated by the MTT assay. Significant difference between cells expressing empty vector and WT, or three mutants at concentration of 35 μM (p<0.05).