Meiosis-dependent tyrosine phosphorylation of a yeast protein related to the mouse p51ferT.

The FER locus of the mouse encodes two mRNA species: one is constitutively transcribed, giving rise to a 94 kDa tyrosine kinase (p94ferT); the second is a meiosis-specific RNA that gives rise to a 51 kDa tyrosine kinase (p51ferT). The p51ferT 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 p51ferT, a 51 kDa phosphotyrosyl protein --p51y-- was identified in Saccharomyces cerevisiae. The p51y 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 p51ferT is ectopically expressed in yeast, it is active, leading to preferential phosphorylation of an approx. 65 kDa protein. A similar pattern of phosphorylation by p51ferT is seen in mammalian cells.