Guanine for DNA synthesis. A compulsory route through ribonucleotide reductase

Duan, Dah-Shuhn; Sadée, Wolfgang

doi:10.1042/bj2551045

Cited by 5 publications

(4 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, these signaling pathways are only the potential downstream targets; the upstream mechanisms that sense the depletion of guanine nucleotide and trigger the cell cycle arrest or apoptosis are still not very clear. Interestingly, it has been shown that certain specific inhibitors of ribonucleotide biosynthesis, including MPA, cause a reversible p53-dependent G 1 arrest, and p53 has been proposed to serve as a sensor of ribonucleotide pool perturbation (20), although MPA has been shown to inhibit DNA synthesis (21,22). p53 has also been shown to mediate the cell cycle arrest and apoptosis in response to guanine nucleotide depletion in human neuroblastoma cell lines (17, 23).…”

Section: Inosine Monophosphate Dehydrogenase (Impdh)mentioning

confidence: 99%

Mycophenolic Acid Activation of p53 Requires Ribosomal Proteins L5 and L11

Sun

Dai

2008

Journal of Biological Chemistry

104

106

View full text Add to dashboard Cite

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is widely used as an immunosuppressive agent. MPA selectively inhibits inosine monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme for the de novo synthesis of guanine nucleotides, leading to depletion of the guanine nucleotide pool. Its chemotherapeutic effects have been attributed to its ability to induce cell cycle arrest and apoptosis. MPA treatment has also been shown to induce and activate p53. However, the mechanism underlying the p53 activation pathway is still unclear. Here, we show that MPA treatment results in inhibition of pre-rRNA synthesis and disruption of the nucleolus. This treatment enhances the interaction of MDM2 with L5 and L11. Interestingly, knockdown of endogenous L5 or L11 markedly impairs the induction of p53 and G 1 cell cycle arrest induced by MPA. These results suggest that MPA may trigger a nucleolar stress that induces p53 activation via inhibition of MDM2 by ribosomal proteins L5 and L11. Inosine monophosphate dehydrogenase (IMPDH)3 is an essential, rate-limiting enzyme for the de novo synthesis of guanine nucleotides. It catalyzes the nicotinamide adenine dinucleotide (NAD)-dependent oxidation of inosine-5Ј-monophosphate (IMP) to xanthosine-5Ј-monophosphate (XMP), which is the committed step in de novo guanine nucleotide biosynthesis (1). This reaction is particularly important to B and T lymphocytes, which are singularly dependent on the de novo pathway, rather than the salvage pathway, for purine biosynthesis (2). There are two separate, but very closely related IMPDH isoenzymes, termed type I and type II, that share 84% amino acid identity (3). Expression of IMPDH, particularly the type II enzyme, is significantly up-regulated in many tumor cells, including leukemia cells (1, 4 -7); thus, IMPDH is a target for cancer as well as immunosuppressive chemotherapy. Inhibitors of IMPDH such as mycophenolate mofetil (MMF, Cellcept), a prodrug of mycophenolic acid (MPA), have been used in organ and stem cell transplantation and in autoimmune diseases as highly effective immunosuppressive agents (8).MPA, the active metabolite of MMF, is a selective inhibitor of IMPDH (8). It can effectively induce cell-cycle arrest in late G 1 phase in lymphocytes (9 -11), and results in differentiation (12-14) or apoptosis (15-18) in cultured cell lines depending on cell type. It has been shown that MPA treatment inhibits the induction of cyclin D3, a major component of cyclin-dependent kinase (CDK), and degradation of p27 kip1 , a CDK inhibitor, resulting in G 1 cell cycle arrest (9). MPA causes apoptosis in interleukin-3-dependent murine hematopoietic cell lines through inhibiting both the Ras-MAPK and mTOR pathways (15). Also, the induction of apoptosis in multiple myeloma cell lines occurs through both caspase-dependent (18) and caspaseindependent (19) mechanisms. However, these signaling pathways are only the potential downstream targets; the upstream mechanisms that sense the depletion of guanine nucleotide and trigger the...

show abstract

Section: Inosine Monophosphate Dehydrogenase (Impdh)mentioning

confidence: 99%

Mycophenolic Acid Activation of p53 Requires Ribosomal Proteins L5 and L11

Sun

Dai

2008

Journal of Biological Chemistry

104

106

View full text Add to dashboard Cite

show abstract

“…The dramatic differences in dGTP accumulation in G1-and S-phase cells can resolve this paradox. G.-phase NSU-1 and dGuo-L cells slowly and extensively accumulate dGTP (for kinetics see [25]), whereas S-phase cells show a much faster turnover rate because of ongoing DNA synthesis, and hence accumulate much less dGTP from dG. Further, we have previously shown that the direct synthesis of dGTP from dG has limited capacity relative to dGTP utilization for DNA synthesis [25].…”

Section: Discussionmentioning

confidence: 99%

“…G.-phase NSU-1 and dGuo-L cells slowly and extensively accumulate dGTP (for kinetics see [25]), whereas S-phase cells show a much faster turnover rate because of ongoing DNA synthesis, and hence accumulate much less dGTP from dG. Further, we have previously shown that the direct synthesis of dGTP from dG has limited capacity relative to dGTP utilization for DNA synthesis [25]. The drastically lower dGTP accumulation in S-phase compared with G,-phase cells is expected to mitigate dG effects specifically in S-phase cells.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanisms of 2′-deoxyguanosine toxicity in mouse T-lymphoma cells with purine nucleoside phosphorylase deficiency and resistance to inhibition of ribonucleotide reductase by dGTP

Duan

Nagashima

Hoshino

et al. 1990

Biochemical Journal

Self Cite

View full text Add to dashboard Cite

Purine nucleoside phosphorylase (PNP; EC 2.4.2.1) deficiency is thought to cause T-lymphocyte depletion by accumulation of dG and dGTP, resulting in feedback inhibition of ribonucleotide reductase (RR; EC 1.17.4.1) and hence DNA synthesis. To test for additional toxic mechanisms of dG, we selected a double mutant of the mouse T-lymphoma S-49 cell line, dGuo-L, which is deficient in PNP and partially resistant to dGTP feedback inhibition of RR. The effects of dG on dGuo-L cells (concn. causing 50 % inhibition, IC50 = 150 1uM) were compared with those on the wild-type cells (IC50 = 30 4M) and the NSU-1 mutant with PNP deficiency only (IC50 = 15 /tM). Fluorescence flow cytometry showed that equitoxic dG concentrations arrested wild-type and NSU-1 cells at the G1-S interface while allowing continued DNA synthesis in the S-phase, whereas the double mutant dGuo-L cells progressed through the cell cycle normally. dGuo-L cells accumulated high levels of dGTP in G,-phase, but not in S-phase cells, because of the utilization of dGTP for DNA synthesis and limited capacity to synthesize dGTP from dG. These results support the hypothesis that dG/dGTP toxicity occurs in the G,-phase or at the G1-S interface. Failure of dG to arrest the double mutant dGuo-L cells at the G1-S interface allows these cells to escape into S-phase, with an accompanying drop in dGTP levels. Thus the partial resistance of dGuo-L cells to dG toxicity may result from their shorter residence time in G1, allowing them to sustain higher dGTP levels. Hence RR inhibition by dGuo may not be the primary toxic mechanism in S-49 cells; rather, it may serve as an accessory event in dG toxicity by keeping the cells in the sensitive phase of the cell cycle. Among the possible targets of dG toxicity is RNA synthesis, which was inhibited at an early stage in dGuo-L cells.

show abstract

Cockayne's syndrome fibroblasts are characterized by hypersensitivity to deoxyguanosine and abnormal DNA precursor pool metabolism in response to deoxyguanosine or ultraviolet light

Squires

Oates

Bouffler

et al. 1992

Somat Cell Mol Genet

View full text Add to dashboard Cite

New cellular traits of Cockayne's syndrome (CS) associated with DNA precursor metabolism have been identified, namely, hypersensitivity to the toxicity of low concentrations of deoxyguanosine (dG) and abnormal changes in deoxyribonucleotide (dNTP) pools in response to dG or UV. dG treatment results in similar ribonucleotide pool changes in wild-type and CS cells, i.e., GTP levels increase at least twofold. However, the changes in the pool size of the purine deoxyribonucleotides are significantly different; in wild-type cells dATP and dGTP pools increase threefold, but remain unchanged in CS. The mechanism by which dG kills CS cells is not clear, but unlike the inherited purine nucleoside phosphorylase deficiency disease, the toxicity of dG is not due to the accumulation of dGTP and the consequent feedback inhibition of ribonucleotide reductase. UV induces different dNTP pool changes in CS and wild-type cells. In wild-type cells dTTP, dCTP, and dATP pools increase three- to fivefold within 4 h of irradiation, while the dGTP pool contracts. In CS cells, only the dGTP pool expands (four- to sixfold), while the other three contract. Each of these new phenotypic traits, together with UV sensitivity, is coordinately corrected in the complementing proliferating CSA x CSB hybrid cells.

show abstract

Guanine for DNA synthesis. A compulsory route through ribonucleotide reductase

Cited by 5 publications

References 16 publications

Mycophenolic Acid Activation of p53 Requires Ribosomal Proteins L5 and L11

Mycophenolic Acid Activation of p53 Requires Ribosomal Proteins L5 and L11

Mechanisms of 2′-deoxyguanosine toxicity in mouse T-lymphoma cells with purine nucleoside phosphorylase deficiency and resistance to inhibition of ribonucleotide reductase by dGTP

Cockayne's syndrome fibroblasts are characterized by hypersensitivity to deoxyguanosine and abnormal DNA precursor pool metabolism in response to deoxyguanosine or ultraviolet light

Contact Info

Product

Resources

About