Control of Histone H4 Gene Transcription in the Sea Urchin Embryo

温伯格博士正在研究两个组蛋白H4基因的转录调控，这两个基因在海胆胚胎中以不同的时间程序表达。早期H4基因在卵裂期和囊胚期转录，在原肠胚中不表达。他正在研究的特定晚期H4基因的表达水平很低，直到胚泡中期，转录显着增加。主要目的是了解这两个基因的差异调控所涉及的控制网络。这些研究应该会为胚胎早期的基因调控提供一个模型。海胆H4组蛋白基因具有许多与脊椎动物H4基因相似的特征，从本文提出的研究中获得的信息应该与其他生物的H4基因调控有关。此外，海胆EH4基因的表达有两个方面特别令人兴奋。首先，该基因的发育控制的主要部分是负面的。包含-150到-140之间10个碱基序列的缺失导致在囊胚后阶段不能抑制转录。该提案的目标之一是了解EH4基因控制的这种模式。第二个特别令人感兴趣的特征是，只有当阳性作用因子UHF-1的结合位点被删除时，转录才需要TATA盒。此外，在体内表达分析中，LH4TATA盒不能替代缺失UHF-1位点的基因中的早期TATA序列。目标之一是研究UHF-1、TFIID和启动子元件如何参与转录的启动。这些实验的一般策略是通过核提取中的转录或通过将基因注射到另一种海胆物种的受精卵中的体内表达试验来鉴定序列元件和测试元件的排列。

Dr. Weinberg is studying the transcriptional regulation of two histone H4 genes which are expressed with different temporal programs in the sea urchin embryo. The early H4 gene is transcribed in the cleavage and early blastula stages and is not expressed at gastrula. The particular late H4 gene he is studying is expressed at a low level until mid-blastula when transcription markedly increases. The major goal is to understand the control network involved in the differential regulation of these two genes. These studies should provide a model for gene regulation at a very early embryonic stage. The sea urchin H4 histone genes have a number of features similar to vertebrate H4 genes and information gained from the research proposed here should be relevant to H4 gene regulation in other organisms. Moveover, there are two aspects of sea urchin EH4 gene expression which are particularly exciting. The first is that a major part of the developmental control of the gene is negative. Deletions which include a 10 bp sequence between -150 and -140 result in a failure to repress transcription at post-blastula stages. One of the goals of the proposal is to understand this mode of EH4 gene control. A second feature which is of special interest is that the TATA box is required for transcription only if the binding site for the positive acting factor UHF-1 is deleted. Moreover, in an in vivo expression assay, the LH4 TATA box cannot substitute for the early TATA sequence in a gene lacking the UHF- 1 site. One of the goals is to investigate how UHF-1, TFIID, and an initiator element are involved in the initiation of transcription. The general strategy of these experiments is to identify sequence elements and test arrangements of the elements by transcription in nuclear extracts or by using an in vivo expression assay in which genes are injected into fertilized eggs of another sea urchin species.