FIGURE 1.

Subcellular localization and function of the eukaryotic LSM complexes. LSM1 protein promotes the assembly of the LSM1-7 complex in the cytoplasm. This complex is a critical component of the decapping machinery and, therefore, plays an essential role in the 5′-3′ mRNA decay pathway. LSM8, however, directs the formation of the LSM2-8 complex in the nucleus. This complex physically interacts with the oligo-U tract of the U6 snRNA to block its degradation by exonucleases. The LSM2-8 complex is a core component of the spliceosome and, coherently, participates in the splicing reaction.