Figure 1. Example of RNA pulldown experiment using synthetic RNA oligonucleotides. (a) The synthetic RNAs that carry either the wild‐type (ATM) or the deleted sequence (ATM Δ); (b) A band‐shift experiment using labeled ATM WT RNA (lane 1, left) incubated in the presence of nuclear extract (lane 2), nuclear extract plus an antibody specific against the U1snRNP U1A protein (lane 3), and a nuclear extract plus a control antibody (lane 4, right). The samples were run on a 6% nondenaturing PAGE gel; (c) A pulldown analysis using the ATM WT (lane 1, left) and ATM Δ (lane 2, right) RNAs bound to the adipic acid dehydrazide beads following incubation with a commercial HeLa nuclear extract. Following the addition of SDS‐PAGE running buffer, the bead‐derived proteins were separated in a 12% denaturing SDS‐PAGE gel and stained with Coomassie blue, according to standard protocols. The bands indicated by arrows refer to the several U1snRNP components that are differentially bound to these two RNAs (U170K, U1A, and SmRNP proteins B and B′), as determined by mass spectrometric analysis.