The cloning and analysis of LEK1 identifies variations in the LEK centromere protein F mitosin gene family

We report the cloning of a novel murine cDNA, LEK1, that is related to huma n CENP-F and mitosin and more distantly to chicken CMF1, The proteins from these three organisms have significant homology, yet differ in their tempor al, spatial, and subcellular localizations. The human proteins bind the kin etochore in mitotic cells, whereas the chicken protein is found only in ske letal and cardiac muscle and is developmentally regulated. Mouse LEK1 is a single copy gene that codes for two developmentally regulated transcripts. The LEK1 protein is expressed early and ubiquitously in mouse development a nd is generally down-regulated as development proceeds in a manner that cor relates to a cessation of mitosis, In adult tissues, the LEK1 protein is de tected exclusively in the pronucleus of the oocyte and was not observed in other actively dividing tissues. Subcellular localization revealed that the LEK1 protein in mitotic cells does not bind the kinetochore, From these da ta, we hypothesize that chicken CMF1, human CENP-F, mitosin, and mouse LEK1 are members of an emerging family of genes that have important and functio nally distinct roles in development and cell division.