Mapping of the bovine genes of the de novo AMP synthesis pathway¹

Abstract

Summary The purine nucleotides adenosine monophosphate (AMP) and guanosine monophosphate (GMP) are critical for energy metabolism, cell signalling and cell reproduction. Despite their essential function, little is known about the regulation and in vivo expression pattern of the genes involved in the de novo purine synthesis pathway. The complete coding region of the bovine phosphoribosylaminoimidazole carboxylase gene (PAICS), which catalyses steps 6 and 7 of the de novo purine biosynthesis pathway, as well as bovine genomic sequences of the six other genes in the pathway producing inosine monophosphate (IMP) and AMP [phosphoribosyl pyrophosphate amidotransferase (PPAT), phosphoribosylglycinamide formyltransferase (GART), phosphoribosylformylglycinamidine synthase (PFAS), adenylosuccinate lyase (ADSL), 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) and adenylosuccinate synthase (ADSS)], were identified. The genes were mapped to segments of six different bovine chromosomes using a radiation hybrid (RH) cell panel. The gene PPAT, coding for the presumed rate-limiting enzyme of the purine de novo pathway was closely linked to PAICS on BTA6. These, and the other bovine locations i.e. GART at BTA1, PFAS at BTA19, ADSL at BTA5, ATIC at BTA2 and ADSS at BTA16, are in agreement with published comparative maps of cattle and man. PAICS and PPAT genes are known to be closely linked in human, rat and chicken. Previously, an expressed sequence fragment of PAICS (Bos taurus corpus luteum, BTCL9) was mapped to BTA13. By isolation and characterization of a BAC clone, we have now identified a PAICS processed pseudogene sequence (psiPAICS) on BTA13. Processed pseudogene sequences of PAICS and other genes of the purine biosynthesis pathway were identified in several mammalian species, indicating that the genes of this pathway have been susceptible to retrotransposition. The seven bovine genes are expressed at a higher level in testicular and ovary tissues compared with skeletal muscle.

A missense mutation in PFAS (phosphoribosylformylglycinamidine synthase) is likely causal for embryonic lethality associated with the MH1 haplotype in Montbéliarde dairy cattle

“…This perfect conservation reveals a strong evolutionary constraint and provides evidence that this residue plays an important role in the stability or activity of the protein. Phosphoribosylformylglycinamidine synthase is involved in the fourth step of the de novo purine synthesis, a universal pathway among eukaryote organisms (with the exception of some para-sites) due to the central function of purine molecules in cell metabolism such as DNA and RNA synthesis and energy molecule supply (Henikoff, 1987;Bønsdorff et al, 2004). Although purine synthesis is a regulated balance between de novo and salvage pathways, it has been shown that de novo synthesis is more active in proliferating cells and therefore essential for meeting the high demand of purines for nucleic acid synthesis in early embryonic development (Alexiou and Leese, 1992).…”

On the Dynamics of the Adenylate Energy System: Homeorhesis vs Homeostasis

“…The ATP consuming-generating system is open and consequently some AMP molecules are de novo biosynthesized [143] ; whilst a part of AMP does not continue in the reactive system due to its hydrolysis, forming adenine and ribose 5-phosphate [144] . Finally, according to experimental observations, we have considered that a very small part of ATP does not remain in the system, but is drained out from the cell [145] – [149] .…”

Knockdown of PAICS inhibits malignant proliferation of human breast cancer cell lines

“…The phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase ( PAICS ) gene encodes a bifunctional enzyme that has phosphoribosylaminoimidazole carboxylase activity in its N-terminal region and phosphoribosylaminoimidazole succinocarboxamide synthetase activity in its C-terminal region [ 3 ]. This enzyme catalyzes steps 6 and 7 of the de novo purine biosynthesis pathway (Phosphoribosyl pyrophosphate amidotransferase (PPAT) catalyses step 1; phosphoribosylglycinamide formyltransferase (GART) steps 2, 3 and 5; phosphoribosylformylglycinamidine synthase (PFAS) step 4; phosphoribosylaminoimidazole carboxylase (PAICS) steps 6 and 7; adenylosuccinate lyase (ADSL) step 8 and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) steps 9 and 10) [ 4 ]. Thus, PAICS is a promising target for rational anticancer drug design [ 3 ].…”