Dataset Information

Proteomic analysis of interchromatin granule clusters.

ABSTRACT: A variety of proteins involved in gene expression have been localized within mammalian cell nuclei in a speckled distribution that predominantly corresponds to interchromatin granule clusters (IGCs). We have applied a mass spectrometry strategy to identify the protein composition of this nuclear organelle purified from mouse liver nuclei. Using this approach, we have identified 146 proteins, many of which had already been shown to be localized to IGCs, or their functions are common to other already identified IGC proteins. In addition, we identified 32 proteins for which only sequence information is available and thus these represent novel IGC protein candidates. We find that 54% of the identified IGC proteins have known functions in pre-mRNA splicing. In combination with proteins involved in other steps of pre-mRNA processing, 81% of the identified IGC proteins are associated with RNA metabolism. In addition, proteins involved in transcription, as well as several other cellular functions, have been identified in the IGC fraction. However, the predominance of pre-mRNA processing factors supports the proposed role of IGCs as assembly, modification, and/or storage sites for proteins involved in pre-mRNA processing.

SUBMITTER: Saitoh N

PROVIDER: S-EPMC491843 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature

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Proteomic analysis of interchromatin granule clusters.

Saitoh Noriko N Spahr Chris S CS Patterson Scott D SD Bubulya Paula P Neuwald Andrew F AF Spector David L DL

Molecular biology of the cell 20040528 8

A variety of proteins involved in gene expression have been localized within mammalian cell nuclei in a speckled distribution that predominantly corresponds to interchromatin granule clusters (IGCs). We have applied a mass spectrometry strategy to identify the protein composition of this nuclear organelle purified from mouse liver nuclei. Using this approach, we have identified 146 proteins, many of which had already been shown to be localized to IGCs, or their functions are common to other alre ...[more]

PMID: 15169873

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Project description:Starch is the primary form of reserve carbohydrate storage in plants. Rice (Oryza sativa L.) is a monocot whose reserve starch is organized into compounded structures within the amyloplast, rather than a simple starch grain (SG). The mechanism governing the assembly of the compound SG from polyhedral granules in apposition, however, remains unknown. To further characterize the proteome associated with these compounded structures, three distinct methods of starch granule preparation (dispersion, microsieve, and flotation) were performed. Phase separation of peptides (aqueous trypsin-shaving and isopropanol solubilization of residual peptides) isolated starch granule-associated proteins (SGAPs) from the distal proteome of the amyloplast and the proximal 'amylome' (the amyloplastic proteome), respectively. The term 'distal proteome' refers to SGAPs loosely tethered to the amyloplast, ones that can be rapidly proteolyzed, while proximal SGAPs are those found closer to the remnant amyloplast membrane fragments, perhaps embedded therein-ones that need isopropanol solvent to be removed from the mature organelle surface. These two rice starch-associated peptide samples were analyzed using nano-liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). Known and novel proteins, as well as septum-like structure (SLS) proteins, in the mature rice SG were found. Data mining and gene ontology software were used to categorize these putative plastoskeletal components as a variety of structural elements, including actins, tubulins, tubulin-like proteins, and cementitious elements such as reticulata related-like (RER) proteins, tegument proteins, and lectins. Delineating the plastoskeletal proteome begins by understanding how each starch granule isolation procedure affects observed cytoplasmic and plastid proteins. The three methods described herein show how the technique used to isolate SGs differentially impacts the subsequent proteomic analysis and results obtained. It can thus be concluded that future investigations must make judicious decisions regarding the methodology used in extracting proteomic information from the compound starch granules being assessed, since different methods are shown to yield contrasting results herein. Data are available via ProteomeXchange with identifier PXD032314.

Dataset Information

Proteomic analysis of interchromatin granule clusters.

Publications

Proteomic analysis of interchromatin granule clusters.

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