Wang Qinhong, Mordukhova Elena A, Edwards Andrea L, Rybenkov Valentin V
University of Oklahoma, Department of Chemistry and Biochemistry, 620 Parrington Oval, Norman, OK 73019, USA.
J Bacteriol. 2006 Jun;188(12):4431-41. doi: 10.1128/JB.00313-06.
MukBEF is a bacterial SMC (structural maintenance of chromosome) complex required for chromosome partitioning in Escherichia coli. We report that overproduction of MukBEF results in marked chromosome condensation. This condensation is rapid and precedes the effects of overproduction on macromolecular synthesis. Condensed nucleoids are often mispositioned; however, cell viability is only mildly affected. The overproduction of MukB leads to a similar chromosome condensation, even in the absence of MukE and MukF. Thus, the non-SMC subunits of MukBEF play only an auxiliary role in chromosome condensation. MukBEF, however, was often a better condensin than MukB. Furthermore, the chromosome condensation by MukB did not rescue the temperature sensitivity of MukEF-deficient cells, nor did it suppress the high frequency of anucleate cell formation. We infer that the role of MukBEF in stabilizing chromatin architecture is more versatile than its role in controlling chromosome size. We further propose that MukBEF could be directly involved in chromosome segregation.
MukBEF是大肠杆菌中染色体分离所需的一种细菌SMC（染色体结构维持）复合体。我们报道，MukBEF的过量表达会导致明显的染色体凝聚。这种凝聚迅速发生，且先于过量表达对大分子合成的影响。凝聚的类核常常定位错误；然而，细胞活力仅受到轻微影响。即使在没有MukE和MukF的情况下，MukB的过量表达也会导致类似的染色体凝聚。因此，MukBEF的非SMC亚基在染色体凝聚中仅起辅助作用。然而，MukBEF通常比MukB是更好的凝聚素。此外，MukB引起的染色体凝聚并不能挽救MukEF缺陷细胞的温度敏感性，也不能抑制无核细胞形成的高频率。我们推断，MukBEF在稳定染色质结构中的作用比其在控制染色体大小中的作用更为多样。我们进一步提出，MukBEF可能直接参与染色体分离。
