Journal Article

The Human GARS-AIRS-GART Gene Encodes Two Proteins Which Are Differentially Expressed during Human Brain Development and Temporally Overexpressed in Cerebellum of Individuals with Down Dyndrome

Gary Brodsky, Tristan Barnes, John Bleskan, Laurence Becker, Marlin Cox and David Patterson

in Human Molecular Genetics

Volume 6, issue 12, pages 2043-2050
Published in print November 1997 | ISSN: 0964-6906
Published online November 1997 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/6.12.2043
The Human GARS-AIRS-GART Gene Encodes Two Proteins Which Are Differentially Expressed during Human Brain Development and Temporally Overexpressed in Cerebellum of Individuals with Down Dyndrome

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Purines are critical for energy metabolism, cell signalling and cell reproduction. Nevertheless, little is known about the regulation of this essential biochemical pathway during mammalian development. In humans, the second, third and fifth steps of de novo purine biosynthesis are catalyzed by a trifunctional protein with glycinamide ribonucleotide synthetase (GARS), aminoimidazole ribonucleotide synthetase (AIRS) and glycinamide ribonucleotide formyltransferase (GART) enzymatic activities. The gene encoding this trifunctional protein is located on chromosome 21. The enzyme catalyzing the intervening fourth step of de novo purine biosynthesis, phosphoribosylformylglycineamide amidotransferase (FGARAT), is encoded by a separate gene on chromosome 17. To investigate the regulation of these proteins, we have generated monoclonal and/or polyclonal antibodies specific to each of these enzymatic domains. Using these antibodies on western blots of Chinese hamster ovary (CHO) cells transfected with the human GARS-AIRS-GART gene, we show that this gene encodes not only the trifunctional protein of 110 kDa, but also a monofunctional GARS protein of 50 kDa. This carboxy-truncated human GARS protein is produced by alternative splicing resulting in the use of a polyadenylation site in the intron between the terminal GARS and the first AIRS exons. The expression of both the GARS and GARS-AIRS-GART proteins are regulated during development of the human cerebellum, while the expression of FGARAT appears to be constitutive. All three proteins are expressed at high levels during normal prenatal cerebellum development while the GARS and GARS-AIRS-GART proteins become undetectable in this tissue shortly after birth. In contrast, the GARS and GARS-AIRS-GART proteins continue to be expressed during the postnatal development of the cerebellum in individuals with Down syndrome.

Journal Article.  5976 words.  Illustrated.

Subjects: Genetics and Genomics

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