STRUCTURE AND FUNCTION OF GENE REGULATORY COMPLEXES

细胞中的基因调控需要基因特异性激活和抑制蛋白、通用转录因子和染色质修饰酶的协同作用。这些酶包括组蛋白乙酰转移酶多蛋白酶复合体，它在翻译后使染色质的组蛋白成分的尾部乙酰化。由于基因活性与细胞内局部的组蛋白乙酰化密切相关，组蛋白乙酰转移酶复合体可能是基因活性的重要共同调节因子。最近的研究发现，这种复合体还含有接头或辅助激活蛋白，加强了组蛋白乙酰化和基因激活之间的关系，并表明染色质修饰和辅助激活功能，如招募到启动子区域，是协调的过程。这些活性可能与人类癌症的发展有关，因为其中一些辅助激活蛋白与细胞癌蛋白和肿瘤抑制基因产物相关联。这项建议的长期目标是将高分辨率结构描述与遗传和生化信息相结合，以了解真核基因调控复合体如何发挥作用。这项建议侧重于酵母组蛋白乙酰转移酶复合体的关键功能的亚复合体。主要目标包括：1.用生化方法分析Ada2/Ada3/Gcn5复合体的结构和功能；2.用X射线结晶学确定Ada2/Ada3/Gcn5三元复合体的三维结构；3.鉴定和结晶与转录激活因子结合的SagA组分；4.表征和结晶与一般转录因子结合的SagA组分。

Gene regulation in cells requires the concerted action of gene specific activator and repressor proteins, general transcription factors, and chromatin modifying enzymes. These enzymes include the histone acetyltransferase multiprotein enzyme complexes which post-translationally acetylate the tails of histone protein components of chromatin. Since gene activity is well correlated with local histone acetylation in the cell, histone acetyltransferase complexes are likely to act as important coregulators of gene activity. The recent findings that such complexes also contain adaptor or coactivator proteins strengthened this relationship between histone acetylation and gene activation, and suggested that chromatin modifications and coactivator functions, such as recruitment to promoter regions, are coordinated processes. These activities may be involved in the development of human cancers since some of these coactivator proteins associate with cellular oncoproteins and tumor suppressor gene products. The long-term objectives of this proposal are to combine high-resolution structural descriptions with genetic and biochemical information to understand how eukaryotic gene regulatory complexes function. This proposal focuses on subcomplexes responsible for crucial functions of the yeast SAGA histone acetyltransferase complex. The primary goals include 1. analyzing the structure and function of the Ada2/Ada3/Gcn5 complex by biochemical methods, 2. determining the three-dimensional structure of the Ada2/Ada3/Gcn5 ternary complex by X-ray crystallography, 3. characterizing and crystallizing SAGA components bound to transcriptional activators and 4. characterizing and crystallizing SAGA components bound to general transcription factors.