Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.
PLoS Genet. 2012;8(5):e1002720. doi: 10.1371/journal.pgen.1002720. Epub 2012 May 24.
The homeotic genes in Drosophila melanogaster are aligned on the chromosome in the order of the body segments that they affect. The genes affecting the more posterior segments repress the more anterior genes. This posterior dominance rule must be qualified in the case of abdominal-A (abd-A) repression by Abdominal-B (Abd-B). Animals lacking Abd-B show ectopic expression of abd-A in the epidermis of the eighth abdominal segment, but not in the central nervous system. Repression in these neuronal cells is accomplished by a 92 kb noncoding RNA. This "iab-8 RNA" produces a micro RNA to repress abd-A, but also has a second, redundant repression mechanism that acts only "in cis." Transcriptional interference with the abd-A promoter is the most likely mechanism.
果蝇中的同源异形基因按照它们影响的身体部位的顺序在染色体上排列。影响更后端节段的基因抑制更前端的基因。在 Abdominal-B (Abd-B) 抑制 Abdominal-A (abd-A) 的情况下，这个后优势规则必须加以限定。缺乏 Abd-B 的动物在第八个腹部节段的表皮中表现出 abd-A 的异位表达，但在中枢神经系统中没有。这些神经元细胞中的抑制是通过一个 92kb 的非编码 RNA 实现的。这种“iab-8 RNA”产生一种 micro RNA 来抑制 abd-A，但也有第二个冗余的抑制机制，仅在“顺式”起作用。转录干扰 abd-A 启动子是最有可能的机制。
