Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MHC class I proteins mediate a variety of functions in antiviral defense. In humans and mice, three MHC class I loci each contribute one or two alleles and each can present a wide variety of peptide Ags. In contrast, many lower vertebrates appear to use a single MHC class I locus. Previously we showed that a single locus was predominantly expressed in the mallard duck (Anas platyrhynchos) and that locus was adjacent to the polymorphic transporter for the Ag-processing (TAP2) gene. Characterization of a genomic clone from the same duck now allows us to compare genes to account for their differential expression. The clone carried five MHC class I genes and the TAP genes in the following gene order: TAP1, TAP2, UAA, UBA, UCA, UDA, and UEA. We designated the predominantly expressed gene UAA. Transcripts corresponding to the UDA locus were expressed at a low level. No transcripts were found for three loci, UBA, UCA, and UEA. UBA had a deletion within the promoter sequences. UCA carried a stop codon in-frame. UEA did not have a polyadenylation signal sequence. All sequences differed primarily in peptide-binding pockets and otherwise had the hallmarks of classical MHC class I alleles. Despite the presence of additional genes in the genome, the duck expresses predominantly one MHC class I gene. The limitation to one expressed MHC class I gene may have functional consequences for the ability of ducks to eliminate viral pathogens, such as influenza.
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PMID:The MHC of the duck (Anas platyrhynchos) contains five differentially expressed class I genes. 1627 26

In many nonmammalian vertebrates, the genomic organization of the MHC class I region leads to biased expression of a single classical MHC class I gene coevolving with TAP transporters, whereas class I genes are poorly expressed. This contrasts to the three codominantly expressed classical MHC class I genes in humans and mice. In a sequenced haplotype from White Pekin duck, Anas platyrhynchos, there is one predominantly expressed MHC class I, UAA, although they have five MHC class I genes in the complex, arranged TAP1-TAP2-UAA-UBA-UCA-UDA-UEA The UAA gene, situated proximal to the TAP2 gene, is expressed at levels 10-fold greater than that of another expressed gene, UDA. Three duck MHC class I genes (UBA, UCA, and UEA) are predicted to be partially or completely inactivated by promoter defects, introduction of in-frame stop codon, or the lack of a polyadenylation signal. In this study, we confirm that UBA, UCA, and UEA are indeed inactivated through genetic defects at the promoter, whereas UAA and UDA have functionally equivalent promoters. To examine promoter accessibility, we performed bisulfite sequencing and show that none of the MHC class I promoters are inactivated by methylation. We determine that UDA is differentially regulated through its 3' untranslated region. Namely, expression of UDA is downregulated by let-7 microRNA, whereas the predominantly expressed MHC class I UAA is not. Regulation of UDA by let-7 microRNA suggests that the lower expression level is maintained for its function in immunity.
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PMID:The Minor MHC Class I Gene UDA of Ducks Is Regulated by Let-7 MicroRNA. 2743 Jul 16