Figure 3. Validation and annotation of CircCCNB1 and novel circular RNAs in human diploid fibroblasts. (A) Illustration of the annotated genomic region of CCNB1, the putative different RNA splicing forms, and the validation strategy for circular exons 6 and 7 (CircCCNB1). Convergent (blue) and divergent (red) primers were designed to amplify the linear or back-splicing products. (B) Total RNA or genomic DNA isolated from 2BS or IMR-90 cells were subjected to polymerase chain reaction (PCR). (C) Upper panel: Red arrow showing the back-splicing of CCNB1 exons 6 and 7 confirmed by Sanger sequencing. Lower panel: CircCCNB1 mature sequence with 378 nt. (D) Total RNA from 2BS or IMR-90 cells with or without RNase-R treatment were subjected to qRT-PCR.