title: A novel role for minimal introns: routing mRNAs to the cytosol.
abstract: BACKGROUND
  Introns and their splicing are tightly coupled with the subsequent mRNA maturation steps, especially nucleocytoplasmic export. A remarkable fraction of vertebrate introns have a minimal size of about 100 bp, while majority of introns expand to several kilobases even megabases in length.
  
  
  RESULTS
  We carried out analyses on the evolution and function of minimal introns (50-150 bp) in human and mouse genomes. We found that minimal introns are conserved in terms of both length and sequence. They are preferentially located toward 3' end of mRNA and non-randomly distributed among chromosomes. Both the evolutionary conservation and non-random distribution are indicative of biological relevance. We showed that genes with minimal introns have higher abundance, larger size, and tend to be universally expressed as compared to genes with only large introns and intron-less genes. Genes with minimal introns replicate earlier and preferentially reside in the vicinities of open chromatin, suggesting their unique nuclear position and potential relevance to the regulation of gene expression and transcript export.
  
  
  CONCLUSIONS
  Based on these observations, we proposed a nuclear-export routing model, where minimal introns play a regulatory role in selectively exporting the highly abundant and large housekeeping genes that reside at the surface of chromatin territories, and thus preventing entanglement with other genes located at the interior locations.
authors.affiliation: CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhu
authors.forename: Fuhong
authors.initials: F
authors.lastname: He
authors.forename: Dapeng
authors.initials: D
authors.lastname: Wang
authors.forename: Kan
authors.initials: K
authors.lastname: Liu
authors.forename: Dawei
authors.initials: D
authors.lastname: Huang
authors.forename: Jingfa
authors.initials: J
authors.lastname: Xiao
authors.forename: Jiayan
authors.initials: J
authors.lastname: Wu
authors.forename: Songnian
authors.initials: S
authors.lastname: Hu
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D005075:Biological Evolution; D002843:Chromatin; D003600:Cytosol / Q000378:metabolism*; D005796:Genes / Q000235:genetics; D016678:Genome; D015894:Genome, Human; D006801:Humans; D007438:Introns / Q000502:physiology*; D051379:Mice; D008957:Models, Genetic; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D002843:Chromatin; D012333:RNA, Messenger