Project description:Erythropoiesis is essential to mammals and is regulated at multiple steps by both extracellular and intracellular factors. Many transcriptional regulatory networks in erythroid differentiation have been well characterized. However, our understanding of post-transcriptional regulatory circuitries in this developmental process is still limited. Using genomic approaches, we identified a sequence-specific RNA-binding protein, Cpeb4, which is dramatically induced in terminal erythroid differentiation (TED) by two erythroid important transcription factors, Gata1/Tal1. Cpeb4 belongs to the cytoplasmic polyadenylation element binding (CPEB) protein family that regulates translation of target mRNAs in early embryonic development, neuronal synapse, and cancer. Using primary mouse fetal liver erythroblasts, we found that Cpeb4 is required for terminal erythropoiesis by repressing the translation of a set of mRNAs highly expressed in progenitor cells. This translational repression occurs by the interaction with a general translational initiation factor, eIF3. Interestingly, Cpeb4 also binds its own mRNA and represses its translation, thus forming a negative regulatory circuitry to limit Cpeb4 protein level. This mechanism ensures that the translation repressor, Cpeb4, does not interfere with the translation of other mRNAs in differentiating erythroblasts. Our study characterized a translational regulatorycircuitry that controls TED and revealed that Cpeb4 is required for somatic cell differentiation. We used microarray to identify mRNAs associated with Cpeb4 in mouse fetal liver erythroblasts. Cpeb4 associated mRNAs were isolated from mouse fetal liver erythroblasts using anti-Cpeb4 antibody for immunoprecipitation followed by RNA extraction. Then Affymetrix microarrays were used to identify and quantify the mRNAs associated with Cpeb4.
Project description:Erythropoiesis is essential to mammals and is regulated at multiple steps by both extracellular and intracellular factors. Many transcriptional regulatory networks in erythroid differentiation have been well characterized. However, our understanding of post-transcriptional regulatory circuitries in this developmental process is still limited. Using genomic approaches, we identified a sequence-specific RNA-binding protein, Cpeb4, which is dramatically induced in terminal erythroid differentiation (TED) by two erythroid important transcription factors, Gata1/Tal1. Cpeb4 belongs to the cytoplasmic polyadenylation element binding (CPEB) protein family that regulates translation of target mRNAs in early embryonic development, neuronal synapse, and cancer. Using primary mouse fetal liver erythroblasts, we found that Cpeb4 is required for terminal erythropoiesis by repressing the translation of a set of mRNAs highly expressed in progenitor cells. This translational repression occurs by the interaction with a general translational initiation factor, eIF3. Interestingly, Cpeb4 also binds its own mRNA and represses its translation, thus forming a negative regulatory circuitry to limit Cpeb4 protein level. This mechanism ensures that the translation repressor, Cpeb4, does not interfere with the translation of other mRNAs in differentiating erythroblasts. Our study characterized a translational regulatorycircuitry that controls TED and revealed that Cpeb4 is required for somatic cell differentiation. We used microarray to identify mRNAs associated with Cpeb4 in mouse fetal liver erythroblasts.
Project description:Retinoblastoma-1 (RB1), and the RB1-related proteins p107 and p130, reside at a central node in the cell cycle regulatory network. RB1 is required for normal erythroid development in vitro, but is largely dispensable for erythropoiesis in vivo. The modest phenotype caused by RB1 deficiency in mice raises questions about redundancy within the RB1 family, and the role of RB1 in erythroid differentiation. Here we show that RB1 is the major pocket protein that regulates terminal erythroid differentiation. Erythroid cells lacking all pocket proteins exhibit the same cell cycle defects as those deficient for RB1 alone. Further, we show that RB1 broadly represses gene expression in erythroid cells, coincident with the transition from precursor to terminally differentiated cell. RB1-repressed genes are well expressed but downregulated at the final stage of erythroid development. By merging differential and time-dependent changes in expression, we define a group of approximately 800 RB1-repressed genes. As anticipated, these genes are enriched for terms such as cell cycle and DNA metabolic process, but also for terms such as mRNA processing, chromosome organization, and ubiquitin-mediated protein catabolic pro-cess. Our results suggest that RB1-mediated repression of genes involved in noncanonical processes has a central role in terminal erythroid differentiation.
Project description:Retinoblastoma-1 (RB1), and the RB1-related proteins p107 and p130, reside at a central node in the cell cycle regulatory network. RB1 is required for normal erythroid development in vitro, but is largely dispensable for erythropoiesis in vivo. The modest phenotype caused by RB1 deficiency in mice raises questions about redundancy within the RB1 family, and the role of RB1 in erythroid differentiation. Here we show that RB1 is the major pocket protein that regulates terminal erythroid differentiation. Erythroid cells lacking all pocket proteins exhibit the same cell cycle defects as those deficient for RB1 alone. Further, we show that RB1 broadly represses gene expression in erythroid cells, coincident with the transition from precursor to terminally differentiated cell. RB1-repressed genes are well expressed but downregulated at the final stage of erythroid development. By merging differential and time-dependent changes in expression, we define a group of approximately 800 RB1-repressed genes. As anticipated, these genes are enriched for terms such as cell cycle and DNA metabolic process, but also for terms such as mRNA processing, chromosome organization, and ubiquitin-mediated protein catabolic pro-cess. Our results suggest that RB1-mediated repression of genes involved in noncanonical processes has a central role in terminal erythroid differentiation.