| Abstract |
Many circular RNAs (circRNAs) are differentially expressed in different tissues or cell types, suggestive of specific factors that regulate their biogenesis. Here, taking advantage of available mutation strains of RNA-binding proteins (RBPs) in Caenorhabditis elegans, I performed a screening of circRNA regulation in 13 conserved RBPs. Among them, loss of FUST-1, the homolog of Fused in Sarcoma (FUS), caused downregulation of multiple circRNAs. By rescue experiments, I confirmed FUST-1 as a circRNA regulator. Through RNA sequencing using circRNA-enriched samples, circRNAs targets regulated by FUST-1 were identified globally, with hundreds of them significantly altered. Furthermore, I showed that FUST-1 regulates circRNA formation with only small to little effect on the cognate linear mRNAs. When recognizing circRNA pre-mRNAs, FUST-1 can affect both exon-skipping and circRNA in the same genes. Moreover, I identified an autoregulation loop in fust-1, where FUST-1, isoform a (FUST-1A) promotes the skipping of exon 5 of its own pre-mRNA, which produces FUST-1, isoform b (FUST-1B) with different N-terminal sequences. FUST-1A is the functional isoform in circRNA regulation. Although FUST-1B has the same functional domains as FUST-1A, it cannot regulate either exon-skipping or circRNA formation. This study provided an in vivo investigation of circRNA regulation, which will be helpful to understand the mechanisms that govern circRNA formation.
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