Change in protein phenotype without a nucleus: translational control in platelets.

For most cells the nucleus takes center stage. Not only is it the largest organelle in eukaryotic cells, it carries most of the genome and transcription of DNA to RNA largely takes place in the nucleus. Because transcription is a major step in gene regulation, the absence of a nucleus is limiting from a biosynthetic standpoint. Consequently, the anucleate status of platelets has stereotyped it as a cell without synthetic potential. It is now clear, however, that this viewpoint is far too simplistic. In response to physiologic stimuli, platelets synthesize biologically relevant proteins that are regulated via gene expression programs at the translational level. This process does not require a nucleus; instead, it uses mRNAs and other translational factors that appear to be retained in specialized fashion as megakaryocytes generate platelets during thrombopoiesis. We highlight the molecular machinery and pathways used by platelets to translate mRNA into protein and offer insight into how these synthesized products may regulate thrombotic and inflammatory events.