Ueta Masami, Ohniwa Ryosuke L, Yoshida Hideji, Maki Yasushi, Wada Chieko, Wada Akira
Department of Physics, Osaka Medical College, Takatsuki, Osaka, Japan.
J Biochem. 2008 Mar;143(3):425-33. doi: 10.1093/jb/mvm243. Epub 2008 Jan 2.
During the stationary phase of growth in Escherichia coli, ribosome modulation factor (RMF) and hibernation promoting factor (HPF) dimerize most 70S ribosomes to form 100S ribosomes. The process of 100S formation has been termed 'ribosomal hibernation'. Here, the contributions of HPF to 100S formation and translation were analysed in vitro. HPF bound to, but did not dimerize the 70S ribosome. RMF dimerized and formed immature 90S ribosomes. Binding of both HPF and RMF converted 90S ribosomes to mature 100S ribosomes, which is consistent with the in vivo data. The role of HPF in in vitro translation also was investigated. In an artificial mRNA poly (U)-dependent phenylalanine incorporation assay, HPF bound to ribosomal particles and inhibited translation. In contrast, in a natural MS2 mRNA-dependent leucine incorporation assay, bound HPF was removed and hardly inhibited normal translation. Multiple alignment and phylogenetic analyses indicates that the hibernation system mediated by the HPF homologue, RMF and 100S ribosome formation may be specific to the proteobacteria gamma group. In contrast, most bacteria have at least one HPF homologue, and these homologues can be classified into three types, long HPF, short HPF and YfiA.
在大肠杆菌生长的稳定期，核糖体调控因子（RMF）和休眠促进因子（HPF）会使大多数70S核糖体二聚化形成100S核糖体。100S核糖体的形成过程被称为“核糖体休眠”。在此，对HPF在体外100S核糖体形成和翻译过程中的作用进行了分析。HPF能与70S核糖体结合，但不会使其二聚化。RMF可使其二聚化并形成不成熟的90S核糖体。HPF和RMF的结合将90S核糖体转化为成熟的100S核糖体，这与体内数据一致。还研究了HPF在体外翻译中的作用。在人工mRNA聚（U）依赖性苯丙氨酸掺入试验中，HPF与核糖体颗粒结合并抑制翻译。相反，在天然MS2 mRNA依赖性亮氨酸掺入试验中，结合的HPF被去除，几乎不抑制正常翻译。多重序列比对和系统发育分析表明，由HPF同源物RMF介导的休眠系统和100S核糖体形成可能特异于γ-变形菌纲。相比之下，大多数细菌至少有一个HPF同源物，这些同源物可分为三种类型，即长HPF、短HPF和YfiA。
