The Ccr4-Not Complex Interacts with the mRNA Export Machinery

Abstract

BackgroundThe Ccr4-Not complex is a key eukaryotic regulator of gene transcription and cytoplasmic mRNA degradation. Whether this complex also affects aspects of post-transcriptional gene regulation, such as mRNA export, remains largely unexplored. Human Caf1 (hCaf1), a Ccr4-Not complex member, interacts with and regulates the arginine methyltransferase PRMT1, whose targets include RNA binding proteins involved in mRNA export. However, the functional significance of this regulation is poorly understood.Methodology/Principal FindingsHere we demonstrate using co-immunoprecipitation approaches that Ccr4-Not subunits interact with Hmt1, the budding yeast ortholog of PRMT1. Furthermore, using genetic and biochemical approaches, we demonstrate that Ccr4-Not physically and functionally interacts with the heterogenous nuclear ribonucleoproteins (hnRNPs) Nab2 and Hrp1, and that the physical association depends on Hmt1 methyltransferase activity. Using mass spectrometry, co-immunoprecipitation and genetic approaches, we also uncover physical and functional interactions between Ccr4-Not subunits and components of the nuclear pore complex (NPC) and we provide evidence that these interactions impact mRNA export.Conclusions/SignificanceTaken together, our findings suggest that Ccr4-Not has previously unrealized functional connections to the mRNA processing/export pathway that are likely important for its role in gene expression. These results shed further insight into the biological functions of Ccr4-Not and suggest that this complex is involved in all aspects of mRNA biogenesis, from the regulation of transcription to mRNA export and turnover.

Identification of <i>ebs1</i>, <i>lsm6</i> and <i>nup159</i> as suppressors of <i>spt</i>10 effects at <i>ADH</i>2 in <i>Saccharomyces cerevisiae</i> suggests post-transcriptional defects affect mRNA synthesis

“…In contrast to the above models, given that CCR4, CAF1, LSM6, NUP159 and EBS1 defects might be expected to have broad affects on the mRNA degradation and/or transport of many genes [39][40][41], it remains possible that the mRNA for certain key transcriptional initiation factors might be specifically sensitive to corresponding defects in mRNA degradation or transport. For instance, the mRNA for holoenzyme or core initiation components might be specifically affected by such defects, resulting again, indirectly, in reduced ADH2 gene expression.…”

“…Given these interactions between mRNA transport and transcription, the NUP159 protein and the CCR4-NOT complex, which has been shown to interact with the mRNA export pathway [40], may exert their respective effects on ADH2 chromatin structure and expression by virtue of their effects on mRNA export. Since the SPT10 protein is specifically involved in affecting chromatin structure [2,35,36], this could be one means by which defects in NUP159 and CCR4-NOT components suppress spt10 effects.…”

Post-Transcriptional Regulation of DNA Damage-Responsive Gene Expression

“…BTG2 interacts with the CNOT7 and CNOT8 subunits of the CCR4-NOT deadenylase complex and facilitates deadenylation of mRNAs (32,33,99,100,163). As indicated earlier, the orthologous complex in yeast contributes to the synthesis and decay of mRNAs (113), so the BTG2-CCR4-NOT complex may similarly affect various stages in mRNA synthesis and maturation as well (70,81). It is likely that other UV-responsive RBPs have yet to be identified.…”

CCR4-NOT2 Promotes the Differentiation and Lipogenesis of 3T3-L1 Adipocytes via Upregulation of PPARγ, CEBPα and Inhibition of P-GSK3α/β and β-Catenin

“…Thus, overexpression of GSK3β phosphorylation inhibited adipogenesis in 3T3-L1 preadipocytes [18] and pharmacological inhibitors of GSK3β blocked adipocyte differentiation [19]. CCR4-NOT complex (CNOT), a large (>2 MDa) multi-complex consisting of eleven subunits is a master regulator of mRNA stability, mRNA export, transcription and translation [20,21]. Among subunits of CCR4-NOT, human CNOT2 regulates the deadenylase activity and structural integrity of the CCR4-NOT complex and controls embryonic development in C. elegans and D. melanogaster [22].…”