Molecular cloning of the human UMP synthase gene and characterization of point mutations in two hereditary orotic aciduria families

Mariko Suchi, Haruo Mizuno, Yoko Kawai, Takashi Tsuboi, Satoshi Sumi, Kazuki Okajima, Mark E. Hodgson, Hisamitsu Ogawa, Yoshiro Wada

Research output: Contribution to journalArticlepeer-review

50 Citations (Scopus)

Abstract

Uridine monophosphate (UMP) synthase is a bifunctional enzyme catalyzing the last two steps of de novo pyrimidine biosynthesis, orotate phosphoribosyltransferase (OPRT) and orotidine-5'-monophosphate decarboxylase (ODC). Loss of either enzymatic activity results in hereditary orotic aciduria, a rare autosomal recessive disorder characterized by retarded growth, anemia, and excessive urinary excretion of orotic add. We have isolated the UMP synthase chromosomal gene from a λEMBL-3 human genomic library and report a single-copy gene spanning ~15 kb. The UMP synthase genomic structure encodes six exons ranging in size from 115 bp to 672 bp, and all splicing junctions adhere to the canonical GT/AG rule. Cognate promoter elements implicated in glucocorticoid- and cAMP-mediated regulation as well as in liver-, myeloid-, and lymphocyte-specific expression are located within the 5' flanking sequence. Molecular investigation of UMP synthase deficiency in a Japanese orotic aciduria patient revealed mutations R96G (A-to-G transition; nt 286) and G429R (G-to-C transversion; nt 1285) in one allele and V109G (T-to-G transversion; nt 326) in the other allele. Expression of human UMP synthase cDNAs containing these mutations in pyrimidine auxotrophic Escherichia coli and in recombinant baculovirus- infected $f21 cells demonstrates impaired activity presumably associated with the urinary orotic acid substrate accumulations observed in vivo. We further establish the identity of two polymorphisms, G213A (v = .26) and 440Gpoly (v = .27) located in exons 3 and 6, respectively, which did not significantly compromise either OPRT or ODC function.

Original languageEnglish
Pages (from-to)525-539
Number of pages15
JournalAmerican Journal of Human Genetics
Volume60
Issue number3
Publication statusPublished - 03-1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Genetics
  • Genetics(clinical)

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