Meiosis-dependent tyrosine phosphorylation of a yeast protein related to the mouse p51^ferT

The FER locus of the mouse encodes two mRNA species: one is constitutively transcribed, giving rise to a 94 kDa tyrosine kinase (p94^ferT); the second is a meiosis-specific RNA that gives rise to a 51 kDa tyrosine kinase (p51^ferT). The p51^ferT RNA and protein accumulate in primary spermatocytes that are in prophase of the first meiotic division. By using polyclonal antibodies directed against synthetic peptides derived from the unique amino-terminus of the mouse p51^ferT, a 51 kDa phosphotyrosyl protein - p51^y - was identified in Saccharomyces cerevisiae. The p51^y protein is constitutively expressed in yeast, but in meiotic cells, concomitantly with commitment to meiotic recombination, its level of phosphorylation on tyrosine residues is increased. A different pattern of phosphorylation is observed on serine residues: at early meiotic times the level is decreased, while in later meiotic time the level increases, reaching the vegetative level. When p51^ferT is ectopically expressed in yeast, it is active, leading to preferential phosphorylation of an approx. 65 kDa protein. A similar pattern of phosphorylation by p51^ferT is seen in mammalian cells.