FIGURE 2.

Sam68 resides within an RNP complex in HeLa cells. A, HeLa cell lysates were left untreated or treated with RNase A and RNase-free DNase I (RQ1 DNase) and fractionated using a Superose 6 column. The presence of Sam68 was analyzed by immunoblotting. RNase A-treated fractions 56–66 were collected, pooled, and concentrated with using a Centricon YM-30. The lysates were divided in two; one was left untreated (−mRNA), and the second was incubated with HeLa total RNA (+mRNA). These cell lysates were subsequently fractionated over a Superose 6 column. B, the specificity of the RNase and DNase treatments was confirmed by incubating pBluescript DNA and total RNA isolated from HeLa cells with the indicated enzyme(s), and the products were separated on 1% agarose gels and visualized by ethidium bromide staining. The 1-kb ladder molecular weight markers (Invitrogen) are shown on the left and the right.