Rat genomic structure of amidophosphoribosyltransferase, cDNA sequence of aminoimidazole ribonucleotide carboxylase, and cell cycle-dependent expression of these two physically linked genes

Iwahana, Hiroyuki; Honda, Soichi; Tsujisawa, Toshiyuki; Takahashi, Yōko; Adzuma, K.; Katashima, Rumi; Yamaoka, Takashi; Moritani, Maki; Yoshimoto, Katsuhiko; Itakura, Mitsuo

doi:10.1016/0167-4781(95)00036-g

Cited by 16 publications

(8 citation statements)

References 23 publications

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“…In contrast, the reserve capacity of de novo synthesis for changing its metabolic rate was relatively high, and could be attained through several regulatory mechanisms including the allosteric activation or inhibition of ATase activity (29,30), the cell cycle-dependent expression of the ATase gene (31), and the relatively short half-life of the ATase protein. 2 Resting human T lymphocytes were reported to meet their metabolic demands via the salvage pathway except during cell growth, while intact de novo synthesis is essential for the proliferation of phetohemagglutinin-stimulated T lymphocytes (32).…”

Section: Discussionmentioning

confidence: 98%

Amidophosphoribosyltransferase Limits the Rate of Cell Growth-linked de Novo Purine Biosynthesis in the Presence of Constant Capacity of Salvage Purine Biosynthesis

Yamaoka

Kondo

Honda

et al. 1997

Journal of Biological Chemistry

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Factors controlling relative flux rates of the de novo and salvage pathways of purine nucleotide biosynthesis during animal cell growth are not fully understood. To examine the relative role of each pathway for cell growth, three cell lines including CHO K1 (a wild-type Chinese hamster ovary fibroblast cell line), CHO ade ؊ A (an auxotrophic cell line deficient of amidophosphoribosyltransferase (ATase), a presumed rate-limiting enzyme of the de novo pathway), and CHO ade ؊ A transfected with human ATase cDNA ( ؊ A؉hATase) resulting in 30 -350% of the ATase activity of CHO K1, were cultured in purine-rich or purine-free media. Based on the enzyme activities of ATase and hypoxanthine phosphoribosyltransferase, the metabolic rate of the de novo and salvage pathways, the rate of cell growth (growth rate) in three cell lines under various culture conditions, and the effect of hypoxanthine infusion on the metabolic rate of the de novo pathway in rat liver, we concluded the following. 1) In ؊ A؉hATase transfectants, ATase activity limits the rate of the de novo pathway, which is closely linked with the growth rate. 2) Purine nucleotides are synthesized preferentially by the salvage pathway as long as hypoxanthine, the most essential source of purine salvage, can be utilized, which was confirmed in rat liver in vivo by hypoxanthine infusion. The preferential usage of the salvage pathway results in sparing the energy expenditure required for de novo synthesis.3) The regulatory capacity of the de novo pathway (about 200%) was larger than that of the salvage pathway (about 20%) with constant hypoxanthine phosphoribosyltransferase activity.Purine nucleotides synthesized via de novo and salvage pathways are indispensable for cell growth through DNA and RNA syntheses and for the ATP energy supply. Interference of purine metabolism has thus been the target of antineoplastic drugs. However, it is unclear which of the two pathways is more important for the supply of purine nucleotides during cell growth. Purine nucleotide synthesis catalyzed by HPRT, 1 the key enzyme of the purine salvage pathway, was reported to be more active than that catalyzed by ATase, the presumed ratelimiting enzyme of the de novo pathway, in many tissues and malignant cells (1, 2). The increased metabolic rate via the de novo pathway and ATase activity are, however, more strongly linked with cell growth and malignant transformation than the metabolic rate via the salvage pathway and HPRT activity (1, 3-7). To interpret this enigma, we investigated the mutual regulation of purine biosynthesis between the de novo and salvage pathways. The cDNA cloning of rat and human ATase (hATase) in our laboratory (8, 9), an ATase-deficient auxotrophic Chinese hamster ovary fibroblast cell line of CHO ade Ϫ A, and CHO ade Ϫ A transfected with hATase cDNA driven by the cytomegalovirus promoter ( Ϫ AϩhATase) enabled us to explore the rate-limiting property of ATase and to study the relationship between the two pathways in three cell lines in two purine-free or two purine-...

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Section: Discussionmentioning

confidence: 98%

Amidophosphoribosyltransferase Limits the Rate of Cell Growth-linked de Novo Purine Biosynthesis in the Presence of Constant Capacity of Salvage Purine Biosynthesis

Yamaoka

Kondo

Honda

et al. 1997

Journal of Biological Chemistry

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“…By contrast, little is known about a possible long-term regulation of enzymes involved in nucleotide biosynthesis at the transcriptional level. A cell cycle dependent expression of the CAD and APRT genes was demonstrated in di erent cell types (Liao et al, 1986;Rao and Davidson, 1988;Rao and Church, 1988;Iwahana et al, 1995), indicating that the expression of these enzymes might be regulated by growth factors. In this study we identi®ed the ADL gene as a novel KGF-regulated gene.…”

Section: Discussionmentioning

confidence: 99%

Growth factor – regulated expression of enzymes involved in nucleotide biosynthesis: a novel mechanism of growth factor action

1999

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Keratinocyte growth factor (KGF) is a potent and speci®c mitogen for epithelial cells, including the keratinocytes of the skin. We investigated the mechanisms of action of KGF by searching for genes which are regulated by this growth factor in cultured human keratinocytes. Using the di erential display RT ± PCR technology we identi®ed the gene encoding adenylosuccinate lyase [EC 4.3 [EC 3.5.2.3]). Expression of all of these enzymes was upregulated after treatment with KGF and also with epidermal growth factor (EGF), indicating that these mitogens stimulate nucleotide production by induction of these enzymes. To determine a possible in vivo correlation between the expression of KGF, EGF and the enzymes mentioned above, we analysed the expression of the enzymes during cutaneous wound repair, where high levels of these mitogens are present. Indeed, we found a strong mRNA expression of all of these enzymes in the EGF-and KGF-responsive keratinocytes of the hyperproliferative epithelium at the wound edge, indicating that their expression might also be regulated by growth factors during wound healing.

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“…Previous findings have demonstrated that de novo purine biosynthesis is closely related to the cell cycle (19,20,25,(30)(31)(32)(33). Studies of other enzyme complexes have suggested that the assembly or disassembly of an enzyme cluster may be correlated with cellular events, such as developmental cues or metabolic states of the cell (33); for example, the replitase, a six-enzyme complex involved in DNA replication, has been shown to exist only during S phase (34).…”

Section: Discussionmentioning

confidence: 99%

Purinosome formation as a function of the cell cycle

Chan¹,

Zhao

Pugh

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The de novo purine biosynthetic pathway relies on six enzymes to catalyze the conversion of phosphoribosylpyrophosphate to inosine 5′-monophosphate. Under purine-depleted conditions, these enzymes form a multienzyme complex known as the purinosome. Previous studies have revealed the spatial organization and importance of the purinosome within mammalian cancer cells. In this study, time-lapse fluorescence microscopy was used to investigate the cell cycle dependency on purinosome formation in two cell models. Results in HeLa cells under purine-depleted conditions demonstrated a significantly higher number of cells with purinosomes in the G 1 phase, which was further confirmed by cell synchronization. HGPRT-deficient fibroblast cells also exhibited the greatest purinosome formation in the G 1 phase; however, elevated levels of purinosomes were also observed in the S and G 2 /M phases. The observed variation in cell cycle-dependent purinosome formation between the two cell models tested can be attributed to differences in purine biosynthetic mechanisms. Our results demonstrate that purinosome formation is closely related to the cell cycle.

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Rat genomic structure of amidophosphoribosyltransferase, cDNA sequence of aminoimidazole ribonucleotide carboxylase, and cell cycle-dependent expression of these two physically linked genes

Cited by 16 publications

References 23 publications

Amidophosphoribosyltransferase Limits the Rate of Cell Growth-linked de Novo Purine Biosynthesis in the Presence of Constant Capacity of Salvage Purine Biosynthesis

Amidophosphoribosyltransferase Limits the Rate of Cell Growth-linked de Novo Purine Biosynthesis in the Presence of Constant Capacity of Salvage Purine Biosynthesis

Growth factor – regulated expression of enzymes involved in nucleotide biosynthesis: a novel mechanism of growth factor action

Purinosome formation as a function of the cell cycle

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