Choi S H, Oh C T, Kim S H, Kim Y T, Jeon S H
Department of Biological Sciences, Konkuk University, Seoul, Korea.
Mol Cells. 2000 Apr 30;10(2):156-61. doi: 10.1007/s10059-000-0156-8.
The Polycomb group (PcG) genes encode repressors of many developmental regulatory genes including homeotic genes and are known to act by modifying chromatin structure through complex formation. We describe how Ultrabithorax (Ubx) expression is affected by the PcG mutants in the visceral mesoderm. Mutant embryos of the genes extra sex combs (esc), Polycomb (Pc), additional sex combs (Asx) and pleiohomeotic (pho) were examined. In each mutation, Ubx was ectopically expressed outside of their normal domains along the anterior-posterior axis in the visceral mesoderm, which is consistent with the effect of PcG proteins repressing the homeotic genes in other tissues. All of these four PcG mutations exhibit complete or partial lack of midgut constriction. However, two thirds of esc mutant embryos did not show Ubx expression in parasegment 7 (PS7). Even in the embryos showing ectopic Ubx expression, the level of Ubx expression in the PcG mutations was weaker than that in normal embryos. We suggest that in PcG mutations the ectopic Ubx expression is caused by lack of PcG repressor proteins, while the weaker or lack of Ubx expression is due to the repression of Ubx by Abd-B protein which is ectopically expressed in PcG mutations as well.
多梳蛋白家族（PcG）基因编码包括同源异型基因在内的许多发育调控基因的阻遏物，已知其通过形成复合物来修饰染色质结构发挥作用。我们描述了在内脏中胚层中，超双胸节基因（Ubx）的表达如何受到PcG突变体的影响。对额外性梳基因（esc）、多梳基因（Pc）、额外性梳相关基因（Asx）和多效同源基因（pho）的突变胚胎进行了检测。在每种突变中，Ubx在内脏中胚层沿前后轴的正常区域之外异位表达，这与PcG蛋白在其他组织中抑制同源异型基因的作用一致。所有这四种PcG突变均表现出中肠收缩完全或部分缺失。然而，三分之二的esc突变胚胎在副节7（PS7）中未显示Ubx表达。即使在显示Ubx异位表达的胚胎中，PcG突变中Ubx的表达水平也比正常胚胎中的弱。我们认为，在PcG突变中，Ubx的异位表达是由于缺乏PcG阻遏蛋白所致，而Ubx表达减弱或缺失是由于Abd - B蛋白的抑制作用，Abd - B蛋白在PcG突变中也会异位表达。
