PT  - JOURNAL ARTICLE
AU  - Xu-Kai Ma
AU  - Meng-Ran Wang
AU  - Chu-Xiao Liu
AU  - Rui Dong
AU  - Gordon G. Carmichael
AU  - Ling-Ling Chen
AU  - Li Yang
TI  - A CLEAR pipeline for direct comparison of circular and linear RNA expression
AID  - 10.1101/668657
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 668657
4099  - http://biorxiv.org/content/early/2019/06/12/668657.short
4100  - http://biorxiv.org/content/early/2019/06/12/668657.full
AB  - Sequences of circular RNAs (circRNAs) produced from back-splicing of exon(s) completely overlap with sequences from cognate linear RNAs transcribed from the same gene loci with the exception of their back-splicing junction (BSJ) sites. Examination of global circRNA expression from RNA-seq datasets generally relies on the detection of RNA-seq fragments spanning BSJ sites, but a direct comparison of circular and linear RNA expression from the same gene loci in a genome-wide manner has remained challenging. This is because quantification of BSJ fragments differs from that of linear RNA expression that uses normalized RNA-seq fragments mapped to the whole gene bodies. Here, we have developed a computational pipeline for circular and linear RNA expression analysis from ribosomal-RNA depleted RNA-seq (CLEAR, https://github.com/YangLab/CLEAR). A new quantitation parameter, FPB (fragments per billion mapped bases), is applied to evaluate circular and linear RNA expression individually by fragments mapped to circRNA-specific BSJ sites or to linear RNA-specific splicing junction (SJ) sites. Then, circular and linear RNA expression are directly compared by dividing FPBcirc by FPBlinear to generate a CIRCscore, which indicates the relative circRNA expression using linear RNA expression as the background. Highly-expressed circRNAs with low cognate linear RNA expression background can be identified for further investigation.