| 1. |
- Spasokukotskaja, T., et al.
(författare)
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Deoxycytidine is salvaged not only into DNA but also into phospholipid precursors
- 1988
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier. - 0006-291X .- 1090-2104. ; 155:2, s. 923-929
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Tidskriftsartikel (refereegranskat)abstract
- Deoxycytidine metabolism was investigated in light density human tonsillar lymphocytes using 5-3H-deoxycytidine as extracellular precursor. A significant portion of the deoxycytidine (more than 50% of ethanol soluble pool) was found to incorporate into dCDP-choline and dCDP-ethanolamine beside the well-known pathway i.e. incorporation into DNA in form of dCMP and dTMP. Hydroxyurea increased the labeling of the deoxyliponucleotides from 5-3H-deoxycytidine in spite of its inhibition of DNA synthesis.
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| 2. |
- Spyrou, Giannis, et al.
(författare)
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Compartmentation of dCTP pools. Evidence from deoxyliponucleotide synthesis
- 1987
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 262:34, s. 16425-16432
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Tidskriftsartikel (refereegranskat)abstract
- The nucleotide fraction of cultured 3T6 and 3T3 mouse fibroblasts contains deoxy-CDP choline and deoxy-CDP ethanolamine as well as the corresponding riboliponucleotides. In permeabilized cells both deoxyliponucleotides were formed from dCTP. In intact cells they could be labeled from [5-3H] deoxycytidine or cytidine via transformation of the nucleosides to dCTP. Their turnover was slow compared to that of dCTP. When rapidly growing 3T3 cells were labeled during 90 min from deoxycytidine the specific activity of dCDP choline was 2.4 times higher than that of dCTP while after labeling from cytidine both nucleotides (and CTP) reached the same specific activity under steady state conditions. Also dCDP ethanolamine was labeled more rapidly from deoxycytidine than from cytidine. Our results suggest that the deoxyliponucleotides were synthesized from a dCTP pool that was labeled preferentially from deoxycytidine. Earlier work (Nicander, B., and Reichard, P. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 1347-1351) had demonstrated synthesis of DNA from a dCTP pool labeled preferentially from cytidine. Taken together our results suggest that deoxyliponucleotides and DNA are synthesized from separate dCTP pools.
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| 3. |
- Spyrou, Giannis, et al.
(författare)
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Dynamics of the thymidine triphosphate pool during the cell cycle of synchronized 3T3 mouse fibroblasts
- 1988
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Ingår i: Mutation research. - : Elsevier. - 0027-5107 .- 1873-135X. ; 200:1-2, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- To investigate whether resting cells of 3T3 mouse fibroblasts carry out de novo synthesis of deoxyribonucleoside triphosphates, we determined the turnover of the thymidine triphosphate pool of G0 cells obtained by starvation of cultures for platelet-derived growth factor. These cells were contaminated by less than 1% S-phase cells. In the absence of deoxyribonucleosides in the medium one million G0 cells contained 5 pmole of dTTP with a turnover of 0.09 pmole/min. S-phase cells in comparison contained a 20 times larger dTTP pool with a more than 200-fold faster turnover. Our results suggest that G0 cells carry out a slow but finite de novo synthesis of deoxyribonucleoside triphosphates to satisfy the cells' requirement for DNA repair and mitochondrial DNA synthesis.
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| 4. |
- Spyrou, Giannis, et al.
(författare)
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Intracellular compartmentation of deoxycytidine nucleotide pools in S phase mouse 3T3 fibroblasts
- 1989
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 264:2, s. 960-964
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Tidskriftsartikel (refereegranskat)abstract
- We labeled mouse 3T3 fibroblasts, synchronized in G0 or S phase, from [3H]cytidine or [3H]deoxycytidine and measured the flow of isotope into and through deoxycytidine nucleotide pools, including the two deoxyliponucleotides dCDP choline and dCDP ethanolamine. Compared to G0 cells, S phase cells had much larger pools with a 20-40-fold faster turnover. The dCTP pool of S phase cells during steady state conditions attained a 6-fold higher specific activity than the pool of G0 cells when labeled from cytidine but a 10-fold lower specific activity when labeled from deoxycytidine. The dCTP pool of G0 cells showed a slow but measurable turnover indicating a limited amount of de novo synthesis also in resting cells. The labeling pattern of dCTP and deoxyliponucleotides of G0 cells was compatible with a simple precursor-product relationship. In S phase cells, however, dCDP choline had a 4-6 times higher specific activity during steady state conditions than dCTP and dCMP when the cells were labeled with [3H]deoxycytidine. We suggest that 3T3 cells contain two distinct intracellular dCTP pools, one labeled preferentially from cytidine and used for DNA replication, the other labeled from deoxycytidine and used for deoxyliponucleotide synthesis. We speculate that the latter pool during S phase may be temporarily sequestered in the cell's membrane fraction before equilibration with the much larger dCTP pool originating in S phase cells from the reduction of CDP.
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