Figure 2.

MT1 effect on L1 retrotransposition is specific to MT1 function. (A) Experimental approach for treatment with melatonin receptor antagonists. Treatment with increasing doses of melatonin receptor antagonist was initiated on the day of transfection (Day 0) and was performed two additional times (Day 1 and 2). G418 selection was initiated on Day 1 and continued for 14 days. (B) Melatonin receptor antagonist S20928 relieves MT1 suppression of L1 retrotransposition in HeLa cells in a dose-dependent manner. L1 retrotransposition in HeLa cells in the presence of the control plasmid is not affected by melatonin receptor antagonist treatment (left panel top row and right panel gray bars), but it is increased when the treatment is combined with MT1 expression (left panel bottom row and right panel black bars). Colony numbers obtained for retrotransposition and toxicity without any treatment with melatonin receptor antagonist are set as 100%. (C) MT1 expression and melatonin receptor antagonist S20928 treatment do not affect cell viability and colony formation in HeLa cells. (D) Melatonin receptor antagonist luzindole relieves MT1 suppression of L1 retrotransposition in HeLa cells without any adverse effect on cell viability and colony formation. Error bars are standard deviation; asterisks indicate statistically significant differences by t-test.