Interaction of mRNP proteins with HeLa mt tRNAs. (A) Western blot analyses. HeLa endogenous hnRNP A1 and H and transiently expressed Flag-tagged SRSF1, SRSF2, and SRSF3 proteins were immunoprecipitated and analyzed by western blotting. Control IPs from nontransfected cells (NT) or without antibody (no AB) are shown. (B) Small RNAs coimmunoprecipitated with Flag-tagged SRSF1, SRSF2, and SRSF3 and hnRNP A1 and H proteins were 3′ end-labeled and analyzed on 6% sequencing gels. (C) SR proteins interact with mt tRNAs. Co-IP of mt tRNAs with Flag-tagged SRSF1, SRSF2, and SRSF3 proteins was monitored by northern blot analyses. (Ext) Input extract (50× dilution). (D) Interaction of HeLa hnRNP A1 and H with mt RNAs. (E) Dynamic association of mRNP proteins with mt tRNAs. HeLa cells nontransfected (hnRNP A1 and H) or transfected with the pFL-SRSF1, pFL-SRSF2, or pFL-SRSF3 expression plasmids were divided into two fractions which were treated or nontreated with ActD. After extract preparation, the transiently expressed Flag-tagged SRSF1, SRSF2, and SRSF3 and endogenous hnRNP A1 and H proteins were immunoprecipitated and the copurified mt tRNAs were analyzed on a sequencing gel.
