| PCI proteins eIF3e and eIF3m define distinct translation initiation factor 3 complexes . : BACKGROUND : PCI / MPN domain protein complexes comprise the 19S proteasome lid , the COP 9 signalosome ( CSN ) , and eukaryotic translation initiation factor 3 ( eIF 3 ) . ^^^ RESULTS : Here , we report the unexpected finding that fission yeast has two distinct eIF 3 complexes sharing common core subunits , but distinguished by the PCI proteins eIF3e and the novel eIF3m , which was previously annotated as a putative CSN subunit . ^^^ CONCLUSION : We propose that the PCI proteins eIF3e and eIF3m define distinct eIF 3 complexes that may assist in the translation of different sets of mRNAs . . ^^^ |