FIGURE 4.

A, immunoprecipitation of polysomes was performed with the indicated antibody. IP was followed by RT-PCR (19 cycles) to detect endogenous ATR, TAF6, IER2, and RACK1 transcripts. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was amplified from the same fractions to confirm that equal amounts of mRNA were present in each immunoprecipitated sample. Three times as much material was used to amplify glyceraldehyde-3-phosphate dehydrogenase as the other transcripts. B, Western blot analysis. RKO cells were stably transfected with either GFP or GFP-hnRNP A18 and exposed (+) or not (−) to UV radiation (14 Jm⁻²). The positions of Chk1, phosphorylated Chk1 (p-Chk1, Ser³¹⁷), ATR, and actin are indicated. Fold induction were measured by densitometry and normalized to actin.