Fig. 2

FECR1 is associated with the development of breast cancer. a Formation of FLI1 exonic circular RNA. FECR1 is formed by back splicing of FLI1 exon 4 to exon 2 and is composed of exons 4-2-3. b Detection of FECR1 circular RNA after RNase R digestion. RNA samples were treated with RNase R to remove linear RNAs. For qPCR normalization, the abundance of FECR1 was calculated by standardizing over the spike DNA control and setting the PBS control as 1. **p < 0.01 as compared with PBS and vector controls. c Sequencing of FECR1. Two FECR1 variants were detected by RT-PCR (left panel). V2 was expressed at very low level. We thus focused on the major form V1. The circular RNA (V1) was amplified with a forward primer (JH2532F) that is located at the end of exon 4 and a reverse primer (JH3273R) at the 5′-region of exon 2. Red arrow: back-splicing site. d Expression of FECR1 in breast cancer cell lines. e Expression of FECR1 in breast cancer tissues. Beta-actin was used as the PCR control