TRANSCRIPTION AND MASKING OF MESSENGER-RNA IN GERM-CELLS - INVOLVEMENT OF Y-BOX PROTEINS

Gametogenesis is directed by various specialized genetic mechanisms wh ich, to a considerable extent, apply to the production of both eggs an d sperm and have been conserved across a wide spectrum of eukaryotic o rganisms. Two key aspects which are discussed here are: germ-cell-spec ific gene transcription; and translational repression (masking) of mRN A accumulated in oocytes and spermatocytes/spermatids. Together, these two processes conspire to deliver often large amounts of essential pr oteins at the appropriate stages of development. It is perhaps not sur prising that recent evidence points to a functional link between trans cription activation and translation repression, both processes being d etermined in the nucleus and involving common components. One set of c omponents which has been studied recently are members of the Y-box fam ily of regulatory proteins Most information of the involvement of Y-bo x proteins in germ cell development comes from studies on amphibian oo cytes and mammalian spermatids. In these cells, Y-box proteins have be en detected as major components of both maternal and paternal mRNP par ticles and have been shown to be instrumental in the masking process. Y-box proteins are also implicated in the regulation of several germ-c ell-specific genes. Possible connections between these processes are d iscussed.