Unknown,Transcriptomics,Genomics,Proteomics

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Temporal transcriptional profiling of growth resumption following polyamine-depletion

ABSTRACT: Polyamines are absolutely required for cell growth and proliferation. While polyamine depletion results in reversible cell cycle arrest, the actual mechanism of growth inhibition is still obscure. This experiment aimed at determining the cellular processes elicited by re-addition of polyamines to polyamine-depleted (growth arrested) cells. In order to reveal the general transcriptional responses to polyamine re-addition, NIH3T3 mouse fibroblasts were first treated with 1mM L-Difluoromethylornithine (DFMO) for 96 hours and then growth stimulated by spermidine. Cells were collected at 0, 30, 60, 120, 240, 360, 480 and 600 min upon addition of spermidine to polyamine-depleted (growth arrested) cells. Total RNA was isolated, reverse-transcribed, fragmented, labeled and hybridized to Affymetrix MoGene 1.0 ST DNA array.

ORGANISM(S): Mus musculus

SUBMITTER: Guy Landau

PROVIDER: E-GEOD-36664 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Polyamines are aliphatic polycations that have emerged as important determinants of cell growth and viability in rapidly proliferating cells, including in the pathogenic protozoan parasite Leishmania donovani. In L. donovani, the polyamine spermidine is synthesized by the successive conversion of ornithine into putrescine (catalyzed by ornithine decarboxylase or ODC) and putrescine into spermidine (catalyzed by spermidine synthase or SPDSYN). Deletion of either ODC (del-odc) or SPDSYN (del-spdsyn) from the L. donovani genome renders these parasites auxotrophic for polyamines and these mutants are impaired in their ability to survive both in culture and within the mammalian host without the addition of exogenous polyamine supplementation. Significantly, del-odc parasites immediately cease proliferation after putrescine is removed from the culture media and perish within two weeks, while spermidine starved del-spdsyn mutants, which retain intracellular putrescine pools, show a slow-growth phenotype, and persist for several weeks in culture. To elucidate the key differences within the proteome of putrescine-starved del-odc cells and spermidine-starved del-spdsyn parasites, a shotgun quantitative proteomics approach was undertaken using TMT labeling and LC-MS/MS analysis. Briefly, three biological replicates each for mid-log phase del-odc and del-spdsyn promastigotes grown in the presence of exogenous putrescine (for del-odc) or spermidine (for del-spdsyn) supplementation were washed to remove the exogenous polyamine supplementation and incubated in polyamine-free media. At 24 and 48 h, cells from each biological replicate were isolated and prepared for tandem mass tag (TMT) labeling and downstream LC-MS/MS analyses. Peptides were identified using a database generated from the reference genome of L. donovani BPK282A1 strain. Changes in relative protein abundance for the polyamine-starved del-odc and del-spdsyn cell lines at 24 and 48 h were calculated by comparing aggregate total reporter ion intensities for each protein to that of the corresponding polyamine-supplemented 0-h timepoint.

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