RESUMO
STAT4 is a transcription factor activated in response to IL-12, and is involved in Th1 cell development. The molecular mechanisms controlling the transcription of the STAT4 gene are however, unclear. Sequence comparison of the 5' flanking regions of human, mouse and pufferfish (Fugu rubripes) Stat4 genes revealed a high frequency of Ikaros (Ik) binding elements in all three species. We then investigated the role of Ik binding elements in the human STAT4 promoter using Jurkat T cells. Transactivation, electrophoretic mobility shift assay and RNA interference-mediated gene knockdown experiments revealed that Ik is involved in the regulation of STAT4 in human T cells.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Linfócitos T/metabolismo , Transativadores/genética , Fatores de Transcrição/metabolismo , Ativação Transcricional/genética , Animais , Sequência de Bases , Sítios de Ligação , Genoma , Hematopoese/genética , Humanos , Fator de Transcrição Ikaros , Células Jurkat , Camundongos , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Interferência de RNA , Fator de Transcrição STAT4 , Takifugu/genética , Transcrição Gênica , Dedos de ZincoRESUMO
The enzyme telomerase is essential for maintaining the ends of linear chromosomes. It plays an important role in cell proliferation, differentiation, tumorigenesis and aging. Telomerase is composed of an RNA subunit (TR) and a reverse transcriptase catalytic subunit (TERT). We report here the cloning and characterization of the gene encoding the TERT subunit from a teleost fish, Fugu rubripes. This is the first fish TERT gene to be cloned. The fugu TERT (fTERT) gene comprises of 16 exons and 15 introns similar to the human TERT (hTERT), and encodes a 1074 amino acid protein. The fTERT protein showed 33% to 35% sequence identity to other vertebrate TERTs, and contained all the signature motifs of the TERT family. Analysis of the promoter region of fTERT showed the presence of several transcription factor binding sites (E2F-1, E-box, ER, Sp1 and USF sites) in common with the hTERT promoter, and whose binding factors are known to regulate hTERT. The fTERT gene is expressed in a variety of tissues, with high expression detected in the gill, testis, and ovary. fTERT expression was detected in an immortalized fugu eye-derived cell line. The level of expression was found to be higher in actively dividing cells and reduced at quiescence, suggesting cell cycle regulation of TERT and possibly telomerase activity, in this cell line.
