CSNK1G1 and hepatocellular carcinoma: We characterized hsa_circ_101555 in HCC cells, and found that it consisted of six exons (exon 1–6, 815 nt) and was derived from the host gene CSNK1G1. Moreover, it was cyclized with the head-to-tail splicing of exon 1 and exon 6 and resisted RNase R treatment, demonstrating its stability compared to linear RNA.