HLH GENE FUNCTION IN NEURONAL CELL DETERMINATION

螺旋-环螺旋(Helix-loop Helix，HLH)蛋白是一个进化保守的蛋白家族。 具有复杂二聚化和DNA结合作用的转录因子 特点。对于果蝇和人类HLH蛋白，都具有高亲和力 DNA结合的异源二聚体在不同的HLH蛋白之间形成。 在果蝇中，发现了一个由10个相互作用的hlh基因组成的系统来控制 神经细胞测定。这10个hlh基因由5个激活子组成。 和5个抑制因子，它们控制着神经元模式的不同子集。 拟议中的研究将检验HLH激活剂的假设 蛋白质的功能是形成DNA结合的同源二聚体和异源二聚体，而且 HLH阻遏蛋白通过与激活蛋白结合来发挥作用 形成非DNA结合的杂二聚体。Hlh蛋白也将被检测。 因为它们能够激活培养的报告基因的转录 细胞。这项HLH蛋白功能的生化分析将 辅以体内候选HLH蛋白调节的分析 靶基因，T5。人促黄体生成素蛋白对T5的转录调控 通过对hlh突变体中T5转录本表达的分析进行验证。在……里面 此外，T5 5‘结构域不同部分缺失的突变体将被 检测T5转录本的表达模式。推定的功能 将通过果蝇P元件的转化来确定调控区域 报告基因受控于T5顺式DNA的这些区域。 HLH蛋白与T5调节DNA的结合也将被检测。一个 最终目标将是对特定部位进行定点突变， 在体外结合HLH蛋白，并可能在体内调节T5。 在人类中，至少有一些人促黄体生成素基因是原癌基因。两个人的HLH 急性淋巴母细胞性白血病患者的基因持续易位 白血病。这些严重的突变可能会扰乱正常的蛋白质- 这些转录因子的蛋白质和蛋白质-DNA相互作用。这个 拟议的研究将确定#年卫生保健系统的特点。 苍蝇；这可能会让我们更好地了解人类系统， 以及它在发育和疾病中的作用。

Helix-loop helix (HLH) proteins are an evolutionarily-conserved family of transcription factors which have complex dimerization and DNA-binding characteristics. For both Drosophila and human HLH proteins, high affinity DNA-binding heterodimers form between different HLH proteins. In flies, a system of 10 interacting HLH genes has been found to control neuronal cell determination. These 10 HLH genes consist of 5 activators and 5 repressors, which control different subsets of the neuronal pattern. The proposed research will test the hypothesis that the HLH activator proteins function to form DNA-binding homodimers and heterodimers, and that the HLH repressor proteins function by binding to the activator proteins to form non-DNA-binding heterodimers. The HLH proteins also will be tested for their ability to activate transcription of reporter genes in cultured cells. This biochemical analysis of HLH protein function will be complemented by analysis of HLH protein regulation of a candidate in vivo target gene, T5. Transcriptional regulation of T5 by HLH proteins will be tested by analysis of T5 transcript expression in HLH mutants. In addition, mutants with different parts of the T5 5' domain deleted will be examined for pattern of T5 transcript expression. Function of putative regulatory regions will be confirmed by P element transformation of flies with reporter genes under control of those regions of the T5 cis DNA. Binding of HLH proteins to T5 regulatory DNA also will be assayed. An eventual goal will be site-directed mutagenesis of specific sites which bind HLH proteins in vitro and are likely to regulate T5 in vivo. In humans, at least some HLH genes are proto-oncogenes. Two human HLH genes are consistently translocated in patients with acute lymphoblastic leukemia. These severe mutations are likely to perturb the normal protein- protein and protein-DNA interactions of these transcription factors. The proposed research will determine the characteristics of the HLH system in flies; this will likely provide a better understanding of the human system, and its role in development and disease.