title: Evidence for conserved post-transcriptional roles of unitary pseudogenes and for frequent bifunctionality of mRNAs.
abstract: BACKGROUND
  Recent reports have highlighted instances of mRNAs that, in addition to coding for protein, regulate the abundance of related transcripts by altering microRNA availability. These two mRNA roles - one mediated by RNA and the other by protein - are inter-dependent and hence cannot easily be separated. Whether the RNA-mediated role of transcripts is important, per se, or whether it is a relatively innocuous consequence of competition by different transcripts for microRNA binding remains unknown.
  
  
  RESULTS
  Here we took advantage of 48 loci that encoded proteins in the earliest eutherian ancestor, but whose protein-coding capability has since been lost specifically during rodent evolution. Sixty-five percent of such loci, which we term 'unitary pseudogenes', have retained their expression in mouse and their transcripts exhibit conserved tissue expression profiles. The maintenance of these unitary pseudogenes' spatial expression profiles is associated with conservation of their microRNA response elements and these appear to preserve the post-transcriptional roles of their protein-coding ancestor. We used mouse Pbcas4, an exemplar of these transcribed unitary pseudogenes, to experimentally test our genome-wide predictions. We demonstrate that the role of Pbcas4 as a competitive endogenous RNA has been conserved and has outlived its ancestral gene's loss of protein-coding potential.
  
  
  CONCLUSIONS
  These results show that post-transcriptional regulation by bifunctional mRNAs can persist over long evolutionary time periods even after their protein coding ability has been lost.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Marques
authors.forename: Jennifer
authors.initials: J
authors.lastname: Tan
authors.forename: Sheena
authors.initials: S
authors.lastname: Lee
authors.forename: Lesheng
authors.initials: L
authors.lastname: Kong
authors.forename: Andreas
authors.initials: A
authors.lastname: Heger
authors.forename: Chris P
authors.initials: CP
authors.lastname: Ponting
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017124:Conserved Sequence; D004285:Dogs; D020869:Gene Expression Profiling; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011544:Pseudogenes; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism*; D012377:Rodentia / Q000235:genetics*
chemical_list: D035683:MicroRNAs; D012333:RNA, Messenger