Molecular Genetics of the Polycomb Group Gene Posterior Sex Combs

果蝇后性梳基因（Psc）是一个多效性基因 发育调控基因 作为Polycomb集团的成员 它是维持基因片段特异性 胚胎决定 我们已经克隆并测序了这个基因 发现它和那些 zeste（Su（z）2）基因的相邻抑制子2和最近的 描述了鼠BMI-1癌基因。 使用多烯的免疫染色 我们发现Psc蛋白是一个基因座特异性的， 一种染色体蛋白质，存在于许多 预期的靶基因。 我们将使用这种染色体染色试验 和生殖系转化来绘制靶DNA序列， 负责染色体结合位点，我们将 确定Psc蛋白是否可以直接结合这些序列 体外 我们将尝试确定蛋白质的功能 与Su（z）2和bmi-1共享的结构域， 嵌合基因与突变体拯救试验的组合，染色体 结合，如果可能的话，体外DNA结合。 我们还将 继续分析Psc的发展功能。 我们 将使用抗体染色和来自增强子陷阱的lacz表达 在缺乏母体和合子Psc功能的胚胎中， 确定它是基因表达的起始还是维持 在几个发育途径中受到影响的模式 由于缺少Psc功能而受到干扰。*/

The Posterior Sex Comb (Psc) gene of Drosophila is a pleiotropic developmental regulatory gene. As a member of the Polycomb group of genes it is essential for the maintenance of segment specific embryonic determination. We have cloned and sequenced this gene and found that it shares a 200 amino acid domain with the neighboring Suppressor Two of zeste (Su(z)2) gene and the recently described murine bmi-1 oncogene. Using immunostaining of polytene chromosomes we have found that the Psc protein is a locus specific chromosomal protein that is found at the location of a number of expected target genes. We will use this chromosome staining assay and germ line transformation to map the target DNA sequences that are responsible for the chromosomal binding site and we will determine if the Psc protein can directly bind to these sequences in vitro. We will attempt to determine the function of the protein domain shared with Su(z)2 and bmi-1 using in vitro mutagenesis and chimeric genes combined with assays for mutant rescue, chromosomal binding, and if possible DNA binding in vitro. We will also continue our analysis of the developmental function of Psc. We will use antibody staining and lacz expression from enhancer traps in embryos that lack both maternal and zygotic Psc function to determine if it is the initiation or maintenance of gene expression patterns that is effected in several of the developmental pathways that are perturbed by a lack of Psc function.***//