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Polysome profiling of the malaria parasite Plasmodium falciparum.

ABSTRACT: In the malaria parasite Plasmodium falciparum, global studies of translational regulation have been hampered by the inability to isolate malaria polysomes. We describe here a novel method for polysome profiling in P. falciparum, a powerful approach which allows both a global view of translation and the measurement of ribosomal loading and density for specific mRNAs. Simultaneous lysis of infected erythrocytes and parasites releases stable, intact malaria polysomes, which are then purified by centrifugation through a sucrose cushion. The polysomes are resuspended, separated by velocity sedimentation and then fractionated, yielding a characteristic polysome profile reflecting the global level of translational activity in the parasite. RNA isolated from specific fractions can be used to determine the density of ribosomes loaded onto a particular transcript of interest, and is free of host ribosome contamination. Thus, our approach opens translational regulation in malaria to genome-wide analysis.

SUBMITTER: Lacsina JR

PROVIDER: S-EPMC3135974 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Polysome profiling of the malaria parasite Plasmodium falciparum.

Lacsina Joshua R JR LaMonte Gregory G Nicchitta Christopher V CV Chi Jen-Tsan JT

Molecular and biochemical parasitology 20110513 1

In the malaria parasite Plasmodium falciparum, global studies of translational regulation have been hampered by the inability to isolate malaria polysomes. We describe here a novel method for polysome profiling in P. falciparum, a powerful approach which allows both a global view of translation and the measurement of ribosomal loading and density for specific mRNAs. Simultaneous lysis of infected erythrocytes and parasites releases stable, intact malaria polysomes, which are then purified by cen ...[more]

PMID: 21605599

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Project description:MudPIT analysis of Plasmodium polysomes. TCA precipitated pellet from Plasmodium falciparum polysomes (~50ug) was solubilized in TRIS-HCl pH8.5 and Urea; reduced and alkylated. The protein suspension was digested overnight using Endoproteinase Lys-C followed by a second overnight digestion at 37°C using Trypsin. Formic acid (5% final) was added to stop the reactions. Sample was loaded on split-triple-phase fused-silica micro-capillary column and placed in-line with linear Velos pro ion-trap mass spectrometer (Thermo Scientific), coupled with quaternary Agilent 1260 series HPLC. Fully automated 10-step chromatography run (for a total of 20 hours) was carried out on the sample. Each full MS scan (400-1600 m/z) was followed by ten data-dependent MS/MS scans. The number of the micro scans was set to 1 both for MS and MS/MS. The dynamic exclusion settings used were as follows: repeat count 2; repeat duration 30s; exclusion list size 500 and exclusion duration 90 sec, the minimum signal threshold was set to 500. The MS/MS dataset was searched using SEQUEST (v.27; rev. 9) against a database of 72358 sequences, consisting of 5487 P. falciparum non-redundant proteins (downloaded from PlasmoDB on 2012-07-12), 30536 H. sapiens non-redundant proteins (downloaded from NCBI on 2012-08-27), 177 usual contaminants (such as human keratins, IgGs, and proteolytic enzymes), and, to estimate false discovery rates, 36179 randomized amino acid sequences derived from each non-redundant protein entry. To account for alkylation by CAM, 57 Da were added statically to cysteine residues and to account for the oxidation of methionine residues to methionine sulfoxide (that can occur as an artifact during sample processing) 16Da were added as a differential modification to methionine residue. Peptide/spectrum matches were sorted, selected using DTASelect/CONTRAST (v 1.9). Proteins had to be detected by 1 peptide with 2 independent spectra, leading to FDRs at the protein and spectral levels of 2.89% and 0.26%, respectively.

Dataset Information

Polysome profiling of the malaria parasite Plasmodium falciparum.

Publications

Polysome profiling of the malaria parasite Plasmodium falciparum.

Similar Datasets

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