Roberts S B, Weisser K E, Childs G
J Mol Biol. 1984 Apr 25;174(4):647-62. doi: 10.1016/0022-2836(84)90088-3.
We have determined the nucleotide sequence of sea urchin (Lytechinus pictus) late stage H3 and H4 histone genes contained on the clone pLpH3H4 -21 and of the early stage H3 gene contained on the plasmid pLpA . Comparison of these differentially regulated histone genes with each other and with other L. pictus late and early stage histone H3 and H4 genes previously sequenced confirms that members of each histone gene family (early and late) are more homologous to each other than they are to members of other histone gene families. The spacer regions between two late H3-H4 gene pairs on the clones pLpH3H4 -19 and pLpH3H4 -21 have diverged to the point where they are no longer homologous. However, comparative analysis of the 5' flanking DNA has identified a sequence 5'C-T-C-A-T-G-T-A-T-T3' upstream of both late H4 genes and another, 5'A-G-A-T-T-C-A3', upstream of both H3 genes. Except for a short conserved sequence near the initiation codon, the transcribed 5' leaders of the late mRNAs differ in length and sequence in the two non-allelic late histone gene pairs. This divergence contrasts with the 95 to 96% conservation found between late histone gene coding sequences. The results suggest that there is intergenic exchange in the germline among members of the late histone gene family and that the unit of exchange is the individual gene rather than the heterotypic dimer which includes the common spacer DNA.
我们已经确定了克隆pLpH3H4 -21上包含的海胆（Lytechinus pictus）晚期H3和H4组蛋白基因以及质粒pLpA上包含的早期H3基因的核苷酸序列。将这些差异调节的组蛋白基因相互比较，并与先前测序的其他海胆晚期和早期组蛋白H3和H4基因进行比较，证实每个组蛋白基因家族（早期和晚期）的成员彼此之间的同源性高于它们与其他组蛋白基因家族成员的同源性。克隆pLpH3H4 -19和pLpH3H4 -21上两个晚期H3-H4基因对之间的间隔区已经分化到不再同源的程度。然而，对5'侧翼DNA的比较分析在两个晚期H4基因上游鉴定出一个序列5'C-T-C-A-T-G-T-A-T-T3'，在两个H3基因上游鉴定出另一个序列5'A-G-A-T-T-C-A3'。除了起始密码子附近的一个短保守序列外，两个非等位晚期组蛋白基因对中晚期mRNA的转录5'前导序列在长度和序列上有所不同。这种差异与晚期组蛋白基因编码序列之间95%至96%的保守性形成对比。结果表明，晚期组蛋白基因家族成员在种系中存在基因间交换，并且交换单位是单个基因，而不是包括共同间隔DNA的异型二聚体。
