Transcriptome analysis reveals PTBP1 as a key regulator of circRNA biogenesis

Circular RNAs (circRNAs) are a class of non-coding RNAs generated through back splicing. High expression of circRNAs is often associated with numerous abnormal cellular biological processes. However, the regulatory factors of circRNAs are not fully understood.

In this study, we identified PTBP1 as a crucial regulator of circRNA biogenesis through a comprehensive analysis of the whole transcriptome profiles across 10 diverse cell lines. Knockdown of PTBP1 led to a significant decrease in circRNA expression, concomitant with a distinct reduction in cell proliferation. To investigate the regulatory mechanism of PTBP1 on circRNA biogenesis, we constructed a minigene reporter based on SPPL3 gene. The results showed that PTBP1 can bind to the flanking introns of circSPPL3, and the mutation of PTBP1 motif impedes the back splicing of circSPPL3. Subsequently, to demonstrate that this observation is not an exception, the comprehensive regulatory effects of PTBP1 on circRNAs were confirmed by miniGFP, reflecting the necessity of the binding site in the flanking introns. Analysis of data from clinical samples showed that both PTBP1 and circRNAs exhibited substantial upregulation in acute myeloid leukemia, further demonstrating a potential role for PTBP1 in promoting circRNA biogenesis under in vivo conditions. Competitive endogenous RNA (ceRNA) network revealed that PTBP1-associated circRNAs participated in biological processes associated with cell proliferation.

In summary, our study is the first to identify the regulatory effect of PTBP1 on circRNA biogenesis and indicates a possible link between PTBP1 and circRNA expression in leukemia.