title: Motif types, motif locations and base composition patterns around the RNA polyadenylation site in microorganisms, plants and animals.
abstract: BACKGROUND
  The polyadenylation of RNA is critical for gene functioning, but the conserved sequence motifs (often called signal or signature motifs), motif locations and abundances, and base composition patterns around mRNA polyadenylation [poly(A)] sites are still uncharacterized in most species. The evolutionary tendency for poly(A) site selection is still largely unknown.
  
  
  RESULTS
  We analyzed the poly(A) site regions of 31 species or phyla. Different groups of species showed different poly(A) signal motifs: UUACUU at the poly(A) site in the parasite Trypanosoma cruzi; UGUAAC (approximately 13 bases upstream of the site) in the alga Chlamydomonas reinhardtii; UGUUUG (or UGUUUGUU) at mainly the fourth base downstream of the poly(A) site in the parasite Blastocystis hominis; and AAUAAA at approximately 16 bases and approximately 19 bases upstream of the poly(A) site in animals and plants, respectively. Polyadenylation signal motifs are usually several hundred times more abundant around poly(A) sites than in whole genomes. These predominant motifs usually had very specific locations, whether upstream of, at, or downstream of poly(A) sites, depending on the species or phylum. The poly(A) site was usually an adenosine (A) in all analyzed species except for B. hominis, and there was weak A predominance in C. reinhardtii. Fungi, animals, plants, and the protist Phytophthora infestans shared a general base abundance pattern (or base composition pattern) of "U-rich-A-rich-U-rich-Poly(A) site-U-rich regions", or U-A-U-A-U for short, with some variation for each kingdom or subkingdom.
  
  
  CONCLUSIONS
  This study identified the poly(A) signal motifs, motif locations, and base composition patterns around mRNA poly(A) sites in protists, fungi, plants, and animals and provided insight into poly(A) site evolution.
authors: Molecular Genetics Laboratory, Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincoln Road, Fredericton, New Brunswick, E3B 4Z7, Canada. Xiu-Qing.Li@agr.gc.ca.
authors: Xiu-Qing
authors: XQ
authors: Li
authors: Quantitative Methods Research Group, Faculty of Business Administration, University of New Brunswick, 7 Macaulay Lane, Fredericton, NB, E3B 5A3, Canada. ddu@unb.ca.
authors: Donglei
authors: D
authors: Du
mesh_terms: D000818:Animals; D001482:Base Composition; D017124:Conserved Sequence; D056890:Eukaryota / Q000145:classification / Q000235:genetics; D019143:Evolution, Molecular; D059372:Nucleotide Motifs; D010944:Plants / Q000145:classification / Q000235:genetics; D011061:Poly A / Q000378:metabolism; D026723:Polyadenylation; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D011061:Poly A