Isolation and characterization of proteins from human lymphocyte nuclei using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and post-source decay analysis

The cell nucleus plays an essential role in all aspects of cell function, including DNA replication, gene transcription, RNA processing and cell division. Within the cell nucleus there are many proteins and peptides that have regulatory roles. Although several higher molecular weight protein components (> 30 kDa) have been identified and characterized, limited information is available for the lower molecular weight components. Nuclei from human peripheral blood lymphocytes were isolated and rapidly characterized by employing a strategy using reversed-phase high-performance liquid chromatography, tryptic digestion, and post-source decay analysis of matrix-assisted laser desorption/ionization (MALDI) ions in combination with database searches. Database searches utilizing molecular weight, proteolytic digest fragments, and peptide sequence results identified known proteins. The results illustrate the usefulness of MALDI as a tool in the characterization of low abundance proteins in the cell nucleus.