Tsui H C, Leung H C, Winkler M E
Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School 77030.
Mol Microbiol. 1994 Jul;13(1):35-49. doi: 10.1111/j.1365-2958.1994.tb00400.x.
The region immediately downstream from the miaA tRNA modification gene at 94.8 min contains the hfq gene and the hflA region, which are important in the bacteriophage Q beta and lambda life cycles. The roles of these genes in bacteria remain largely unknown. We report here the characterization of two chromosomal hfq insertion mutations. An omega (omega) cassette insertion near the end of hfq resulted in phenotypes only slightly different from the parent, although transcript mapping demonstrated that the insertion was completely polar on hflX expression. In contrast, an equally polar omega cassette insertion near the beginning of hfq caused pronounced pleiotropic phenotypes, including decreased growth rates and yields, decreased negative supercoiling of plasmids in stationary phase, increased cell size, osmosensitivity, increased oxidation of carbon sources, increased sensitivity to ultraviolet light, and suppression of bgl activation by hns mutations. hfq::omega mutant phenotypes were distinct from those caused by omega insertions early in the miaA tRNA modification gene. On the other hand, both hfq insertions interfered with lambda phage plaque formation, probably by means of polarity at the hflA region. Together, these results show that hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA-region are in the amiB-mutL-miaA-hfq-hflX superoperon.
位于94.8分钟处的miaA tRNA修饰基因下游紧邻区域包含hfq基因和hflA区域，它们在噬菌体Qβ和λ的生命周期中很重要。这些基因在细菌中的作用在很大程度上仍不清楚。我们在此报告了两个染色体hfq插入突变的特征。在hfq末端附近插入一个ω盒，导致的表型与亲本仅略有不同，尽管转录图谱显示该插入对hflX表达完全具有极性。相比之下，在hfq起始处附近插入一个同样具有极性的ω盒会导致明显的多效性表型，包括生长速率和产量降低、稳定期质粒负超螺旋减少、细胞大小增加、渗透敏感性增加、碳源氧化增加、对紫外线敏感性增加以及hns突变对bgl激活的抑制作用。hfq::ω突变体表型与miaA tRNA修饰基因早期ω插入所导致的表型不同。另一方面，两个hfq插入都干扰了λ噬菌体的噬菌斑形成，可能是通过hflA区域的极性作用。总之，这些结果表明hfq功能在大肠杆菌生理学中起着基本作用，并且hfq和hflA区域位于amiB-mutL-miaA-hfq-hflX超级操纵子中。
