Many lncRNA transcripts, similarly to mRNAs, are 5′-capped, polyadenylated, frequently spliced with conventional GT-AG intron excision, and readily evident in cytoplasmic polyA + RNA preparations; thousands of lncRNAs have been discovered from cDNA libraries [5], although abundant nuclear and polyA- lncRNAs have also been identified [6]. Up to one-third of polyA + lncRNAs encoded in the human genome may not be evolutionary conserved beyond primates [4]. In contrast, the majority of human protein-coding genes have pan-mammalian, and usually pan-vertebrate, conservation, many with homologs identifiable throughout metazoa. It has been suggested that non-conserved lncRNAs comprise a part of the molecular basis of species phenotypic uniqueness, distinguishing closely related species from one another by providing substrates for exaptation as well as adaptive evolution [7]. Despite their frequent lack of conservation, overwhelming evidence of lncRNA functions has emerged: they are characterized by diverse, positive and negative, nuclear and cytoplasmic, epigenetic and post-transcriptional regulatory modalities. Documented lncRNA functions include: positive regulation of sense mRNA translation by an antisense lncRNA [8], trans-repression of mRNAs by repeat-containing lncRNAs through the Stauffen-1 mRNA decay pathway [9]; epigenetic
