Predominant identification of RNA-binding proteins in Fas-induced apoptosis by proteome analysis.

Proteome analysis of Jurkat T cells was performed in order to identify proteins that are modified during apoptosis. Subtractive analysis of two-dimensional gel patterns of apoptotic and nonapoptotic cells revealed differences in 45 protein spots. 37 protein spots of 21 different proteins were identified by peptide mass fingerprinting using matrix-assisted laser desorption/ionization mass spectrometry. The hnRNPs A0, A2/B1, A3, K, and R; the splicing factors p54(nrb), SRp30c, ASF-2, and KH-type splicing regulatory protein (FUSE-binding protein 2); and alpha NAC, NS1-associated protein 1, and poly(A)-binding protein 4 were hitherto unknown to be involved in apoptosis. The putative cleavage sites of the majority of the proteins could be calculated by the molecular masses and isoelectric points in the two-dimensional electrophoresis gel, the peptide mass fingerprints, and after translation by treatment with recombinant caspase-3. Remarkably, 15 of the 21 identified proteins contained the RNP or KH motif, the best characterized RNA-binding motifs.