Characterization of new circular RNA products from the Pax-5 gene in B-cells

Abstract

Abstract Circular RNAs (circRNAs) represent a new class of RNAs which are highly expressed and conserved in mammalian cells. CircRNAs regulate many biological processes and their aberrant expression is often associated with disease progression. We have identified and characterized circRNAs generated from the Pax-5 gene, an essential transcription factor for B-cell lineage commitment and also, a potent oncogene. Given the pivotal role of Pax-5 gene products in B-cell development and function, we set out to profile Pax-5 circular RNA (circPax5) expression and elucidate their role in B-cell biology. We identify and map five major circPax5 transcript isoforms which are found in B-cell lines and primary B-cells isolated from peripheral blood mononuclear cells (PBMCs) of healthy donors. These circPax5 variants consists of circular single-stranded RNA sequences corresponding to: i) exons 2–3; ii) exons 2–4; iii) exons 2–5; iv) exons 2–6; and, v) exons 2–8 of the human Pax-5 gene. Using TaqMan assays designed to target each unique circPax5 junction region, we found that circPax5 expression profiles vary with B-cell developmental stages. Furthermore, circPax5 exons 2–5 and 2–6 are overexpressed in patients suffering from chronic lymphocytic leukemia (CLL). Functionally, we observe that circPax5 products modulate B-cell processes and interact by sponging of specific micro-RNAs. Altogether, we identify new genetic products (i.e. circRNAs) generated from a prominent immune-regulating gene (Pax-5). The functional elucidation of circPax5 products will potentially bring insight into the function and signaling of B-cell processes and disease.