We thank Eran Segal, Howard Chang and Yue Wan for their useful advice regarding the PARS-seq protocol. We thank Mali Salmon-Divon for useful advice regarding the splicing analysis. We thank Tirza Doniger for helping us with the data. The work of O.S. was done in partial fulfillment of the requirements of the Faculty of Life-Sciences, Bar-Ilan University, Israel. this work was supported by the Varda and Boaz Dotan Research Center in Hemato-oncology affiliated to the Tel Aviv University, the Canadian Institute of Health Research joint Canada-Israel health research Grant No. 108188-001, the Flight Attendant Medical Research Institute (FAMRI), Israeli Centers of Research Excellence (I-CORE), ISF Gene Regulation in Complex Human Disease Center, ISF Chromatin and RNA Gene Regulation Center. G.R. holds the Djerassi Chair in Oncology, Tel Aviv University, Israel. Author contributions O.S. performed the bioinformatic, structural and statistical assays, analyzed the data, and wrote the manuscript. A.D.S. and K.C. preformed siRNA and nuclease assays, prepared the PARS-seq libraries, and wrote the manuscript. H.T.P. and E.Y.L. preformed the hyper-editing analysis. V.-M.M. preformed the siRNA assays and prepared the Ribo-seq samples. O.M. and N.S.-G. preformed the Ribo-seq experiment. N.K. performed bioinformatics analysis. S.F.-B. and E.G.-S. helped in the preparation of the PARS-seq libraries. Y.L. preformed the RNA-seq and Ribo-seq experiments. N.A. and R.U. conceived ideas and helped writing the manuscript. I.G. helped with the functional bioinformatics and participated in writing the manuscript. E.E. and G.R. designed the experiments, analyzed the data, conceived ideas and wrote the article.