Figure 1.

Binding of L1 RNA to PSF protein in vitro. Binding of (A) biotin-labeled negative RNA probe or (B) biotin-labeled L1 RNA to PSF protein or E. coli total protein measured by electrophoretic mobility shift assay. (C) Increasing amounts of competitive unlabeled L1 RNA or negative control RNA were added followed by incubation for 20 min. (D) RIP assay was performed to test the binding of L1 RNA and PSF protein by transient transfection of L1 RNA and PSF-coded plasmid for 48 h. The enrichment folds of immunoprecipitated L1 RNA were identified by comparing the products of the RIP assay using anti-PSF antibodies with those using normal rabbit IgG. **P<0.01. PSF, polypyrimidine tract-binding protein-associated splicing factor; IgG, immunoglobulin G; L1, long interspersed nuclear element 1; RIP, RNA immunoprecipitation; E. coli, Escherichia coli.