STKE In nucleated cells, noncoding introns are removed from pre-messenger RNA (pre-mRNA) transcripts by the spliceosome (a nuclear complex of proteins and RNAs) before export of the mRNA from the nucleus. Thus, one would not expect that platelets—anucleate blood cells that bud from megakaryocytes—would contain spliceosome components or pre-mRNAs. Nevertheless, Denis et al. show that components of the spliceosome are present in the cytoplasm of human megakaryocytes and also in circulating platelets. Interleukin-1β (IL-1β) pre-mRNA is present in the cytoplasm of quiescent platelets, whereas platelets that had been activated by adhesion to fibrinogen in the presence of thrombin contain mature IL-1β mRNA and protein. Moreover, IL-1β pre-mRNA could be converted into mature mRNA by a platelet extract. Thus, pre-mRNA splicing is a key regulatory point for cytokine production during platelet activation. — EMA Cell 122 , 379 (2005).