Fig. 5. Molecular characterization of pig-1. (A) Schematic diagram of the pig-1 transcript. White boxes represent exons, and the location of the SL1-splice leader is indicated. The terminal intron of pig-1 contains two genes, depicted as grey arrows, that are transcribed in the opposite orientation to pig-1. (B) Schematic diagram of the domain architecture of the PIG-1 protein, depicting the N-terminal kinase domain (unshaded) and the C-terminal kinase-associated domain (black). The locations and identities of the gm300, gm301 and gm280 missense mutations are shown above the diagram. Below the diagram is a table comparing each domain in PIG-1 to orthologs in frog, fish, mouse and human. (C) Phylogenetic relationship of PIG-1 to selected members of the PAR-1/SAD-1/Kin1 superfamily of serine/threonine kinases. PIG-1 clusters with other MELK family members.