Circular RNAs Are the Predominant Transcript Isoform from Hundreds of Human Genes in Diverse Cell Types
HeLa whole cells lysates were fractioned into cytoplasmic and nuclear. The nuclear localized noncoding RNA XIST served as a control for fractionation:, and as expected, was enriched in the nuclear fraction. In addition, precursor ribosomal RNA bands were present in the nucleus but not the cytoplasm (see Figure S4). Using probes specific to each canonical and circular isoform (corresponding to those examples depicted in Figure 3), we compared Ct values calculated from qPCR on cDNA from the cytoplasmic fraction to the Ct value from qPCR on cDNA from the nuclear fraction. Bar heights show this average Ct value difference across 2 biological replicates. Error bars represent 2.5 standard deviations computed from biological variation of the qPCR assay. These results show that most circular isoforms are more enriched in the cytoplasm compared to the canonical linear isoforms.