RESUMO
Regulation of gene expression at the level of transcriptional elongation has been shown to be important in stem cells and tumour cells, but its role in the whole animal is only now being fully explored. Neural crest cells (NCCs) are a multipotent population of cells that migrate during early development from the dorsal neural tube throughout the embryo where they differentiate into a variety of cell types including pigment cells, cranio-facial skeleton and sensory neurons. Specification of NCCs is both spatially and temporally regulated during embryonic development. Here we show that components of the transcriptional elongation regulatory machinery, CDK9 and CYCLINT1 of the P-TEFb complex, are required to regulate neural crest specification. In particular, we show that expression of the proto-oncogene c-Myc and c-Myc responsive genes are affected. Our data suggest that P-TEFb is crucial to drive expression of c-Myc, which acts as a 'gate-keeper' for the correct temporal and spatial development of the neural crest.
Assuntos
Ciclina T/genética , Quinase 9 Dependente de Ciclina/genética , Regulação da Expressão Gênica no Desenvolvimento , Genes myc , Crista Neural/embriologia , Fator B de Elongação Transcricional Positiva/genética , Elongação da Transcrição Genética , Proteínas de Xenopus/genética , Xenopus laevis/embriologia , Animais , Ciclina T/deficiência , Quinase 9 Dependente de Ciclina/deficiência , Isoxazóis/farmacologia , Leflunomida , Morfolinos/farmacologia , Fator B de Elongação Transcricional Positiva/deficiência , Proteínas Proto-Oncogênicas c-myc/biossíntese , RNA Polimerase II/metabolismo , Fatores de Transcrição SOXE/biossíntese , Fatores de Transcrição SOXE/genética , Elongação da Transcrição Genética/efeitos dos fármacos , Transcrição Gênica , Proteínas de Xenopus/deficiência , Xenopus laevis/genéticaRESUMO
The positive transcription elongation factor b (P-TEFb) is essential for the elongation of transcription and cotranscriptional processing by RNA polymerase II. In mammals, it contains predominantly the C-type cyclin cyclin T1 (CycT1) or CycT2 and cyclin-dependent kinase 9 (Cdk9). To determine if these cyclins have redundant functions or affect distinct sets of genes, we genetically inactivated the CycT2 gene (Ccnt2) using the beta-galactosidase-neomycin gene (beta-geo) gene trap technology in the mouse. Visualizing beta-galactosidase during mouse embryogenesis revealed that CycT2 is expressed abundantly during embryogenesis and throughout the organism in the adult. This finding was reflected in the expression of CycT2 in all adult tissues and organs. However, despite numerous matings of heterozygous mice, we observed no CycT2(-/-) embryos, pups, or adult mice. This early lethality could have resulted from decreased expression of critical genes, which were revealed by short interfering RNAs against CycT2 in embryonic stem cells. Thus, CycT1 and CycT2 are not redundant, and these different P-TEFb complexes regulate subsets of distinct genes that are important for embryonic development.