title: Patterns in interspecies similarity correlate with nucleotide composition in mammalian 3'UTRs.
abstract: Post-transcriptional regulation and the formation of mRNA 3' ends are crucial for gene expression in eukaryotes. Interspecies conservation of many sequences within 3'UTRs reveals selective constraint due to similar function. To study the pattern of conservation within 3'UTRs, we compiled and aligned 50 sets of complete orthologous 3'UTRs from four orders of mammals. We observed a mosaic pattern of conservation, with alternating regions of high (phylogenetic footprints) and low similarity. Conservation in 3'UTRs correlates with their base composition and also with the synonymous substitution rate in corresponding coding regions. The non-uniform distribution of conservation is more pronounced for 3'UTRs with a moderate or low level of overall conservation, where invariant nucleotides are more numerous, and their runs of lengths 4-7 occur more frequently than if conservation were random. Many runs of invariant nucleotides are AU-rich or pyrimidine-rich. Some of these runs coincide with known functional cis- elements of eukaryotic mRNAs, such as the U-rich upstream element, polyadenylation signal and DICE regulatory signal. More divergent regions of multiple alignments of 3'UTRs are often more G- and/or C-rich. Our results provide evidence on the importance of moderately conserved regions in 3'UTRs and suggest that regulatory functions of 3'UTRs might utilize gene-specific information in these regions.
authors.affiliation: National Center for Biotechnology Information, National Institutes of Health, 8600 Rockville Pike, Building 38A, Bethesda, MD 20894, USA. shabalin@ncbi.nlm.nih.gov
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Shabalina
authors.forename: Aleksey Y
authors.initials: AY
authors.lastname: Ogurtsov
authors.forename: David J
authors.initials: DJ
authors.lastname: Lipman
authors.forename: Alexey S
authors.initials: AS
authors.lastname: Kondrashov
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics*; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000235:genetics; D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D017124:Conserved Sequence / Q000235:genetics; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D005136:Eye Proteins / Q000235:genetics; D006801:Humans; D008322:Mammals / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012044:Regression Analysis; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D020413:3' Untranslated Regions; D005136:Eye Proteins; D012333:RNA, Messenger; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C517431:PDE6B protein, human