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Figure 3 | Mobile DNA

Figure 3

From: Feedback inhibition of L1 and alu retrotransposition through altered double strand break repair kinetics

Figure 3

Toxicity in cells undergoing constitutive L1 expression. (A) Constitutive L1 open reading frame (ORF)2 expression in HeLa Cells results in lower sensitivity to transient L1 expression. To measure the toxicity of L1 expression, a plasmid expressing a neomycin-resistance cassette was cotransfected with a vector expressing either L1 ORF2 or full length L1 in HeLa ORF2 or HeLa ORF2 ER-- cells. Colony formation was used as a measure of toxicity as previously described [21]. The relative number of G418 resistant (G418r) colonies in the two cell lines was measured in triplicate for cotransfection of full length L1 and L1 ORF2. (B) Constitutive L1 ORF2 expression in HeLa Cells does not alter sensitivity to ionizing radiation. HeLa ORF2 and HeLa ORF2 ER-- cells were exposed to four different doses of ionizing radiation. After exposure, cells were grown for 3 days and the relative numbers of viable cells were measured. Data are means and SD (error bars) of six independent measurements. Asterisks signify a significant (Student t-test, P ≤ 0.0001) difference from the number of G418r colonies seen in HeLa ORF2 cells. (C) Constitutive L1 ORF2 Expression in HeLa cells does not alter cellular proliferation rates. HeLa ORF2 and HeLa ORF2 ER-- cells were seeded, harvested by trypsinization after 1, 2 or 3 days of growth, and viable cells counted. Data are means and SD (error bars) of three independent measurements.

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