RESUMO
Cell cycle withdrawal involves several transcription factors such as E2Fs members that play a key role in cell growth control. Here we describe a novel putative bZIP transcription factor isolated from the retina and involved in neuronal proliferation arrest at the terminal differentiation: PATF (Proliferation Arrest Transcription Factor). We show that PATF associates with E2F4 protein and interacts with the E2F consensus site. PATF expression increases with establishment of quiescent state. Furthermore, the nuclear PATF localization like E2F4, depends on cell growth arrest. The decrease of PATF amount, using a retroviral antisense strategy, results in pursued neuroretina cell mitosis. Our results indicate that PATF could be a new molecular signal implicated in the final neuronal cell cycle withdrawal.
Assuntos
Proteínas Aviárias , Neurônios/citologia , Retina/embriologia , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Fatores de Transcrição de Zíper de Leucina Básica , Divisão Celular , Núcleo Celular/metabolismo , Embrião de Galinha , Clonagem Molecular , Sequência Consenso , DNA Antissenso/farmacologia , Proteínas de Ligação a DNA/metabolismo , Fator de Transcrição E2F4 , Proteínas do Olho/genética , Proteínas do Olho/fisiologia , Humanos , Dados de Sequência Molecular , Neurônios/metabolismo , Células PC12 , RNA Mensageiro/biossíntese , Coelhos , Ratos , Retina/citologia , Fatores de Transcrição/metabolismo , Ativação Transcricional , Células Tumorais CultivadasRESUMO
In this report, we describe the involvement of the quail neuroretina 1 (QN1) protein in retinal development. The Qn1 cDNA was isolated as a gene specifically expressed at the onset of neuronal cell cycle withdrawal (Bidou et al., Mech. Dev. 43 (1993) 159). Qn1 is located in the cytoplasm in proliferating cells during the early stages of the development. Its distribution changes, becoming predominantly nuclear, in neurons during establishment of the quiescent state upon the differentiation. We decreased the amount of QN1 protein by an antisense strategy in vitro or in vivo. This decrease of the amount of QN1 protein results in additional mitosis and in severe abnormalities such as retinal dysplasia. Our results suggest that QN1 plays a key role at the onset of neuronal cell cycle withdrawal.
Assuntos
Proteínas do Olho/química , Proteínas do Olho/fisiologia , Retina/embriologia , Motivos de Aminoácidos , Sequência de Aminoácidos , Animais , Western Blotting , Bromodesoxiuridina/metabolismo , Diferenciação Celular , Divisão Celular , Núcleo Celular/metabolismo , Embrião de Galinha , Proteínas Cromossômicas não Histona/metabolismo , Citoplasma/metabolismo , DNA Complementar/metabolismo , Eletroforese em Gel de Poliacrilamida , Proteínas do Olho/biossíntese , Biblioteca Gênica , Imuno-Histoquímica , Cinética , Microscopia Confocal , Microscopia de Fluorescência , Mitose , Dados de Sequência Molecular , Oligonucleotídeos Antissenso/metabolismo , Estrutura Terciária de Proteína , Codorniz , Retina/anormalidades , Retina/metabolismo , Retroviridae/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The product of the proto-oncogene p56lck is a non-receptor tyrosine kinase member of the Src family. It is found in T cells (Marth et al., 1985, 1988) and in the mouse brain (Omri et al., 1996; Van Tan et al., 1996). In this report, we describe experiments showing that Lck is present in the mouse retina neurons. Lck gene expression was identified after isolating and sequencing the specific 5' and 3' part of the cDNA obtained by RT-PCR. In adult retina Lck immunoreactivity was most abundant in photoreceptor cells and within the outer plexiform layers. Staining was also observed in the inner nuclear and plexiform layers. In transgenic mice, the disruption of the Lck gene had serious consequences on the organization of the retina causing retinal dysplasia. These mice have partial retinal detachment with infolding and rosette formation in the photoreceptor sheet. These retinal abnormalities observed in Lck deficient mice lead to the loss of normal architecture of the photoreceptor and the inner nuclear layers, and provide an important role of Lck protein in the retina development. The lack of the Lck protein produces a spectrum of retinal pathology that resembles human retinopathy of prematurity (ROP).