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The Ccr4-Not complex is a conserved multi-subunit complex in eukaryotes that carries 2 enzymatic activities: ubiquitination mediated by the Not4 RING E3 ligase and deadenylation mediated by the Ccr4 and Caf1 orthologs. This complex has been implicated in all aspects of the mRNA life cycle, from synthesis of mRNAs in the nucleus to their degradation in the cytoplasm. More recently the complex has also been implicated in many aspects of the life cycle of proteins, from quality control during synthesis of peptides, to assembly of protein complexes and protein degradation. Consistently, the Ccr4-Not complex is found both in the nucleus, where it is connected to transcribing ORFs, and in the cytoplasm, where it was revealed to be both associated with translating ribosomes and in RNA processing bodies. This functional and physical presence of the Ccr4-Not complex at all stages of gene expression raises the question of its fundamental role. This review will summarize recent evidence designing the Not3/5 module of the Ccr4-Not complex as a functional module involved in coordination of the regulation of gene expression between the nucleus and the cytoplasm.

International audience; In the fission yeast Schizosaccharomyces pombe, formation of pericentromeric heterochromatin involves RNA interference (RNAi). Recent data indicate that two RNAi complexes, RITS (RNA-induced transcriptional silencing complex) and RDRC (RNA-directed RNA polymerase complex), their respective enzymatic activity, and RNA polymerase II are essential for RNAi-mediated heterochromatin formation. At the site where heterochromatin formation takes place, RNA polymerase II synthesizes an RNA that would serve as an RNA platform to recruit in a siRNA-dependent manner RITS and RDRC, and thereby initiate heterochromatin assembly. Once recruited, RITS and RDRC seem to also contribute to the processing of the RNA platform. Therefore, RNAi-driven heterochromatin assembly appears to take place through a dynamic process of RNA synthesis, RNA-dependant recruitment of RNAi complexes and RNA degradation that all occur in cis. Chez la levure Schizosaccharomyces pombe, l'assemblage d'h?rochromatine p?centrom?que implique l'interf?nce par l'ARN (iARN). Des donn? r?ntes indiquent que deux complexes de l'iARN, RITS ("RNA-induced transcriptional silencing complex") et RDRC ("RNA-directed RNA polymerase complex"), leur activit?nzymatique respective, ainsi que l'ARN polym?se II sont au coeur du processus de formation d'h?rochromatine guid?ar l'iARN. Au niveau de la r?on ?h?rochromatiniser", l'ARN polym?se II synth?se un ARN, qui servirait de plate-forme pour recruter RITS et RDRC ?a chromatine, et initier la formation d'h?rochromatine. Une fois recrut? RITS et RDRC semblent ?lement participer activement ?a d?adation de l'ARN plate-forme. Ainsi, l'assemblage d'h?rochromatine guid?ar l'iARN mettrait en jeu en cis un processus dynamique de synth? d'ARN, de recrutement ARN-d?ndant de complexes de l'iARN, et de d?adation d'ARN.

The nucleosome, fundamental unit of chromatin, is composed of four basic histones, H2A, H2B, H3 and H4, around which DNA is wrapped. In order to have access to DNA, cells must modify the structure of chromatin by different known mechanisms. One such mechanism is by replacing canonical histones in the nucleosome with variants, which can confer special functions to chromatin. H2A.Z is an evolutionary conserved variant of H2A that has both a positive and a negative role on gene transcription. The mechanisms by which H2A.Z acts are still poorly understood. However, recent reports have shed some light on this subject. H2A.Z is found associated with almost 2/3 of the promoters of genes in yeast, suggesting that this histone could have a global role on gene expression by poising chromatin for activation. We review here recent literature and discuss different aspects of the biology of this histone variant.