Kremer H, Hennig W
Department of Molecular and Developmental Genetics, Katholieke Universiteit, Nijmegen, The Netherlands.
Nucleic Acids Res. 1990 Mar 25;18(6):1573-80. doi: 10.1093/nar/18.6.1573.
Histone genes in D. hydei are organized in tandemly repeated clusters., accomodating in total 120-140 repeat units. We cloned one of the repeat units and analysed the nucleotide sequence. The repeat unit has a size of 5.1 x 10(3) base-pairs and contains one copy of each of the genes coding for the core histones and one copy coding for the histone H1. In the promoter regions of the genes we identified the presumptive cap sites and TATA boxes. Two additional sequence elements are shared by all five Drosophila hydei histone genes in the cluster. The sequence CCCTCT/G1 is found in the region upstream of the presumptive CAP sites. The sequence element AGTGAA occurs downstream of the presumptive cap sites and is, in contrast to the promoter element, also seen in the histone genes of Drosophila melanogaster. Cell-cycle dependent regulation of transcription of the Drosophila histone genes may be different from that in other eukaryotes since sequence elements involved in the regulation of cell-cycle dependent transcription are absent. Also other regulatory elements for transcription differ from those of other genes. The highly conserved H1-specific promoter sequence AAACACA and the H2B specific promoter sequence ATTTGCAT, which are involved in the cell-cycle dependent transcription of those histone genes in eukaryotes, are missing in the Drosophila genes. However at the 3' end of the genes the palindrome and the purine-rich region, both conserved sequence elements in histone genes of eukaryotes, are present. The spacer regions show a simple sequence organization. The silent site substitution rate between the coding regions of the D. hydei and D. melanogaster histone genes is at least 1.5 times higher for Drosophila than for sea urchin histone genes.
海德氏果蝇中的组蛋白基因串联排列成重复簇，总共包含120 - 140个重复单元。我们克隆了其中一个重复单元并分析了核苷酸序列。该重复单元大小为5.1×10³碱基对，包含编码核心组蛋白的每个基因的一个拷贝以及编码组蛋白H1的一个拷贝。在基因的启动子区域，我们确定了推定的帽位点和TATA框。该簇中的所有五个海德氏果蝇组蛋白基因共享另外两个序列元件。序列CCCTCT/G1出现在推定帽位点上游区域。序列元件AGTGAA出现在推定帽位点下游，与启动子元件不同的是，它在黑腹果蝇的组蛋白基因中也可见。果蝇组蛋白基因转录的细胞周期依赖性调控可能与其他真核生物不同，因为缺乏参与细胞周期依赖性转录调控的序列元件。此外，其他转录调控元件也与其他基因的不同。真核生物中那些组蛋白基因的细胞周期依赖性转录所涉及的高度保守的H1特异性启动子序列AAACACA和H2B特异性启动子序列ATTTGCAT在果蝇基因中缺失。然而，在基因的3'端，回文序列和富含嘌呤的区域这两个真核生物组蛋白基因中的保守序列元件是存在的。间隔区呈现出简单的序列组织。海德氏果蝇和黑腹果蝇组蛋白基因编码区之间的沉默位点替换率至少是果蝇组蛋白基因相对于海胆组蛋白基因的1.5倍。
