3 research outputs found
Aspects de la régulation de la kinase Cdc2-cycline B dans les ovocytes de Xénope
MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF
Initial activation of cyclin-B1–cdc2 kinase requires phosphorylation of cyclin B1
At the G(2)/M transition of the cell cycle, the cdc25c phosphatase dephosphorylates inhibitory residues of cdc2, and cyclin-B–cdc2 kinase (MPF) is activated. Phosphorylation of cyclin B1 induces its nuclear accumulation, and, since cdc25c is also believed to accumulate and activate shortly before G(2)/M in the nucleus, it has been proposed that this induces cyclin-B1–cdc2 kinase activation. We demonstrate that cyclin B1 phosphorylation has another essential function in vivo: it is required for cdc25c and MPF activation, which does not require nuclear accumulation of cyclin B1, and occurs in the cytoplasm
SCEP1 and SCEP2 are two new components of the synaptonemal complex central element
International audienceThe synaptonemal complex (SC) is a proteinaceous structure that forms between homologous chromosomes during meiosis prophase. The SC is widely conserved across species, but its structure and roles during meiotic recombination are still debated. While the SC central region is made up of transverse filaments and central element proteins in mammals and fungi, few central element proteins have been identified in other species. Here we report the identification of two coiled-coil proteins, SCEP1 and SCEP2, that form a complex and localize at the centre of the Arabidopsis thaliana SC. In scep1 and scep2 mutants, chromosomes are aligned but not synapsed (the ZYP1 transverse filament protein is not loaded), crossovers are increased compared with the wild type, interference is lost and heterochiasmy is strongly reduced. We thus report the identification of two plant SC central elements, and homologues of these are found in all major angiosperm clades