RESUMO
Activator protein-1 (AP-1) is an important bZIP transcription factor that regulates a series of physiological processes by specifically activating transcription of several genes, and one of its well-chartered functions in mammals is participating in bone mineralization. We isolated and cloned the complete cDNA of a Jun/AP-1 homolog from Pinctada fucata and called it Pf-AP-1. Pf-AP-1 had a highly conserved bZIP region and phosphorylation sites compared with those from mammals. A tissue distribution analysis showed that Pf-AP-1 was ubiquitously expressed in P. fucata and the mRNA level of Pf-AP-1 is extremely high in mantle. Pf-AP-1 expression was positively associated with multiple biomineral proteins in the mantle. The luciferase reporter assay in a mammalian cell line showed that Pf-AP-1 significantly up-regulates the transcriptional activity of the promoters of KRMP, Pearlin, and Prisilkin39. Inhibiting the activity of Pf-AP-1 depressed the expression of multiple matrix proteins. Pf-AP-1 showed a unique expression pattern during shell regeneration and pearl sac development, which was similar to the pattern observed for biomineral proteins. These results suggest that the Pf-AP-1 AP-1 homolog is an important transcription factor that regulates transcription of several biomineral proteins simultaneously and plays a role in P. fucata biomineralization, particularly during pearl and shell formation.
Assuntos
Calcificação Fisiológica/genética , Regulação da Expressão Gênica , Pinctada/genética , Pinctada/metabolismo , Fator de Transcrição AP-1/metabolismo , Ativação Transcricional , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA Complementar , Regulação da Expressão Gênica no Desenvolvimento , Dados de Sequência Molecular , Fases de Leitura Aberta , Especificidade de Órgãos/genética , Filogenia , Transporte Proteico , RNA Mensageiro/genética , Fator de Transcrição AP-1/química , Fator de Transcrição AP-1/genética , TranscriptomaRESUMO
Biomineralization is an important and ubiquitous process in organisms. The shell formation of mollusks is a typical biomineral physical activity and is used as a canonical model in biomineralization research. Most recent studies focused on the identification of matrix proteins involved in shell formation; however, little is known about their transcriptional regulation mechanism, especially the transcription factors involved in shell formation. In this study, we identified a homolog of the YY-1 transcriptional factor from Pinctada fucata, named Pf-YY-1, and characterized its expression pattern and biological functions. Pf-YY-1 has a typical zinc finger motif highly similar to those in humans, mice, and other higher organisms, which indicated its DNA-binding capability and its function as a transcription factor. Pf-YY-1 is ubiquitously expressed in many tissues, but at a higher level in the mantle, which suggested a role in biomineralization. The expression pattern of Pf-YY-1 during pearl sac development was quite similar to, and was synchronized with, those of Prisilkin-39, ACCBP, and other genes involved in biomineralization, which also suggested its function in biomineralization.
Assuntos
Pinctada/genética , Fator de Transcrição YY1/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA Complementar/genética , Perfilação da Expressão Gênica , Células HEK293 , Humanos , Camundongos , Minerais/metabolismo , Dados de Sequência Molecular , Filogenia , Pinctada/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homologia de Sequência de Aminoácidos , Fator de Transcrição YY1/metabolismoRESUMO
As a prototype of the TGF-ß superfamily cytokines, TGF-ß is well known for its diverse roles in embryogenesis and adult tissue homeostasis. TGF-ß evokes cellular responses by signaling mainly through cell membrane receptors and transcription factor R-Smads and Co-Smad (Smad4), while an inhibitory Smad, Smad7, acts as a critical negative regulator of TGF-ß signaling. Smad7 antagonizes TGF-ß signaling by regulating the stability or activity of the receptors or blocking the DNA binding of the functional R-Smad-Smad4 complex in the nucleus. However, the function of Smad7 in the nucleus is not fully understood. Yin Yang 1 (YY1) is a ubiquitously expressed transcription factor with multiple functions. It has been reported that YY1 can inhibit Smad-dependent transcriptional responses and TGF-ß/BMP-induced cell differentiation independently of its DNA binding ability. In this study, we found that Smad7 interacts with YY1 and the interaction is attenuated by TGF-ß signaling. Reporter assays and target gene expression analyses revealed that Smad7 and YY1 act in concert to inhibit TGF-ß-induced transcription in the nucleus. Furthermore, Smad7 could enhance the interaction of YY1 with the histone deacetylase HDAC1. Consistently, YY1 and HDAC1 augmented the transcription repression activity of Smad7 in Gal4-luciferase reporter analysis. Therefore, our findings define a novel mechanism of Smad7 and YY1 to antagonize TGF-ß signaling.