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Circular RNAs (circRNAs) from pre-mRNA back-splicing have been recently re-discovered genome-wide in metazoans by taking advantage of RNA deep-sequencing (RNA-seq) of the non-polyadenylated transcriptomes and specific computational pipelines that can retrieve the non-colinear back-splicing junction reads [1-5]. Despite being inefficiently processed and mostly expressed at a low level [1, 2, 6-8], some circRNAs are derived from genomic loci associated with human diseases [9], and increasing lines of evidence have suggested their potential roles in transcriptional, post-transcriptional and translational regulation [10]. However, nothing is known about whether these exceptionally stable circRNAs can be retrotranscribed, and ultimately inserted back into the host genome as processed pseudogenes. Theoretically, a linear mRNA-derived pseudogene keeps the same sequential order (colinear) of exons as …