The ubiquitin system in gametogenesis

Ubiquitin is a ubiquitous and highly conserved protein of 76 amino acid res idues, that can be covalently attached to cellular acceptor proteins. The a ttachment of ubiquitin to target proteins is achieved through a multi-step enzymatic pathway, which involves activities of ubiquitin-activating E1 enz ymes, ubiquitin-conjugating E2 enzymes, and ligating E3 enzymes. Mono- or p oly-ubiquitination of proteins can lead to protein degradation or modificat ion of protein activity. Many components of the complex ubiquitin system sh ow remarkable evolutionary conservation, from yeast to mammalian species. T he ubiquitin system is essential to all eukaryotic cells. Among others, sev eral signal transduction cascades show involvement of the ubiquitin system, but there are currently little data supporting a specific role of the ubiq uitin system in hormonal control of reproduction. Interestingly, during gam etogenesis, many specialized and important aspects of the ubiquitin system become apparent. Components of the ubiquitin system appear to be involved i n different steps and processes during gametogenesis, including control of meiosis, and reorganization of chromatin structure. (C) 1999 Elsevier Scien ce Ireland Ltd. All rights reserved.