Houben A, Belyaev N D, Leach C R, Timmis J N
Department of Genetics, The University of Adelaide, Australia.
Chromosome Res. 1997 Jun;5(4):233-7. doi: 10.1023/B:CHRO.0000032297.10876.86.
Differences are demonstrated between A (transcriptionally active) and B (transcriptionally inactive) chromosomes that are characterized by a different level of histone H4 acetylation and a different timing of DNA replication. These differences between the chromatin of A and B chromosomes were found after immunolabelling of chromsomes of Brachycome dichromosomatica with antibodies specific for different acetylated forms (lysine 5, 8, 12 and 16) of histone H4. In contrast to the A chromosomes, which are labelled brightly in their entirety, the transcriptionally inactive B chromosomes are faintly labelled with antibodies against H4Ac5 and H4Ac8. No such difference between the chromosomes is found after immunostaining with the other antibodies H4Ac12 and H4Ac16. Analysis of DNA replication timing in root-tip meristems suggests that B chromosomes are labelled late in S-phase compared with A chromosomes. After C-banding the B chromosome appeared to have a similar amount of heterochromatin to the A chromosomes.
A（转录活跃）染色体和B（转录不活跃）染色体之间存在差异，其特征在于组蛋白H4乙酰化水平不同以及DNA复制时间不同。在用针对组蛋白H4不同乙酰化形式（赖氨酸5、8、12和16）的特异性抗体对二色短角草染色体进行免疫标记后，发现了A染色体和B染色体染色质之间的这些差异。与完全被明亮标记的A染色体不同，转录不活跃的B染色体被抗H4Ac5和H4Ac8抗体微弱标记。在用其他抗体H4Ac12和H4Ac16进行免疫染色后，未发现染色体之间存在这种差异。对根尖分生组织中DNA复制时间的分析表明，与A染色体相比，B染色体在S期后期被标记。经C带处理后，B染色体似乎具有与A染色体相似数量的异染色质。
