The human gamma-globin TATA and CACCC elements have key, distinct roles in suppressing beta-globin gene expression in embryonic/fetal development

The competition model of globin gene regulation states that the gamma-globin gene precludes expression of the beta-globin gene in early development by competing for the enhancing activity of the locus control region. The gamma-globin gene with a -161 promoter is sufficient for suppressing beta-globin gene expression, and the gamma-globin TATA and CACCC elements are necessary for this effect. In this work, stable transfection and transgenic mouse assays have been performed with constructs containing HS3 and HS2 from the locus control region, the gamma-globin gene with promoter mutation(s), and the beta-globin gene. The data indicate that the gamma-globin TATA and CACCC elements together have at least an additive effect on the beta/gamma-globin mRNA ratio in early erythroid cells, suggesting that the elements work coordinately to suppress beta-globin gene expression. The TATA and CACCC are the major gamma-globin promoter elements responsible for this effect. Transgenic mouse experiments indicate that the gamma-globin TATA element plays a role in gamma-globin expression and beta-globin suppression in the embryo and fetus; in contrast, the CACCC element has a stage-specific effect in the fetus. The results suggest that, as is true for the erythroid Krüppel-like factor (EKLF) and the beta-globin promoter CACCC, a protein(s) binds to the gamma-globin CACCC element to coordinate stage-specific gene expression.     

Regulation of the Discoidin I gamma gene in Dictyostelium discoideum: identification of individual promoter elements mediating induction of transcription and repression by cyclic AMP.

We dissected the promoter of the developmentally induced and cyclic AMP-repressed discoidin I gamma gene and identified a sequence element essential for developmental induction. Transfer of the element to an inactive heterologous promoter demonstrated that this sequence is sufficient to confer expression in axenically growing cells and to induce gene activity in development after growth on bacteria. A 16-base-pair sequence within this element was shown to be sufficient for induction in the discoidin promoter context and was used to reactivate different truncated promoter constructs. This led to the localization of an element necessary for down regulation of gene expression by extracellular cyclic AMP.     

香蕉rbcS基因启动子的克隆及序列分析

以巴西香蕉为材料,根据已经获得的香蕉1,5-二磷酸核酮糖羧化/加氧酶小亚基基因的全长cDNA序列设计1对专一引物,通过PCR扩增得到了香蕉1,5-二磷酸核酮糖羧化/加氧酶小亚基的基因组全长,序列长811 bp,含有2个内含子。根据其基因组序列设计引物,采用SEFA-PCR方法,以总DNA为模板克隆了香蕉1,5-二磷酸核酮糖羧化/加氧酶小亚基基因的启动子序列,长1 681 bp。用PLACE软件分析发现该序列具有启动子的基本元件TATA-box、CAAT-box,包含多个胁迫诱导元件,如光诱导元件、赤霉素、低温诱导元件、昼夜节律调控元件等。该序列的克隆与分析为进一步研究香蕉1,5-二磷酸核酮糖羧化/加氧酶小亚基基因的表达调控奠定了基础。     

真核生物启动子研究概述

启动子是调控基因表达的重要基因元件,它的调控作用是多层次多因素共同作用的结果。通过启动子的调控能够控制基因表达的水平、部位及方式。深入研究启动子对于了解生物的生长发育、防御系统、疾病等都有非常重要的意义。本文综述了启动子克隆、生物信息学分析和预测的方法,比较了两种启动子分析方法,介绍了启动子甲基化、多态性和合成启动子的研究进展,以期能够为启动子的研究提供参考。