RESUMO
The SIL gene expression is increased in multiple cancers and correlates with the expression of mitotic spindle checkpoint genes and with increased metastatic potential. SIL regulates mitotic entry, organization of the mitotic spindle and cell survival. The E2F transcription factors regulate cell cycle progression by controlling the expression of genes mediating the G1/S transition. More recently, E2F has been shown to regulate mitotic spindle checkpoint genes as well. As SIL expression correlates with mitotic checkpoint genes, we hypothesized that SIL is regulated by E2F. We mined raw data of published experiments and performed new experiments by modification of E2F expression in cell lines, reporter assays and chromatin immunoprecipitation. Ectopic expression or endogenous activation of E2F induced the expression of SIL, while knockdown of E2F by shRNA, downregulated SIL expression. E2F activated SIL promoter by reporter assay and bound to SIL promoter in vivo. Taken together these data demonstrate that SIL is regulated by E2F. As SIL is essential for mitotic entry, E2F may regulate G2/M transition through the induction of SIL. Furthermore, as silencing of SIL cause apoptosis in cancer cells, these finding may have therapeutic relevance in tumors with constitutive activation of E2F.
Assuntos
Fator de Transcrição E2F1/fisiologia , Regulação da Expressão Gênica/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Mitose/genética , Animais , Sequência de Bases , Primers do DNA , Drosophila melanogaster , Humanos , Reação em Cadeia da Polimerase , Transcrição Gênica/fisiologiaRESUMO
The SIL gene undergoes a site-specific rearrangement with the SCL gene in 25% of patients with T cell acute lymphoblastic leukemia (ALL). The functional result of this rearrangement is that the SIL regulatory elements aberrantly drive expression of the SCL gene. We have cloned and sequenced the human SIL promoter, cloned a murine homolog, found the sequence to be highly conserved, and defined a minimal promoter region. Both the cloned murine and human sequences were found to be highly active in either human or murine cells. SCL mRNA, driven by a cloned SIL promoter, could be downregulated by DMSO in stably transfected F4-6 murine erythroleukemia cells. The SIL promoter was found to be partially unmethylated in proliferating tissues, in which it is highly expressed, and more highly methylated in post-mitotic tissues, in which SIL is not expressed. The isolation of the SIL promoter provides an important tool for the study of both the SIL gene expression as well as the role of the SIL promoter in leukemogenesis.
