The RNA-binding protein HF-I, known as a host factor for phage Qbeta RNA replication, is essential for rpoS translation in Escherichia coli.
Tóm tắt
The rpoS-encoded sigma(S) subunit of RNA polymerase in Escherichia coli is a global regulatory factor involved in several stress responses. Mainly because of increased rpoS translation and stabilization of sigma(S), which in nonstressed cells is a highly unstable protein, the cellular sigma(S) content increases during entry into stationary phase and in response to hyperosmolarity. Here, we identify the hfq-encoded RNA-binding protein HF-I, which has been known previously only as a host factor for the replication of phage Qbeta RNA, as an essential factor for rpoS translation. An hfq null mutant exhibits strongly reduced sigma(S) levels under all conditions tested and is deficient for growth phase-related and osmotic induction of sigma(S). Using a combination of gene fusion analysis and pulse-chase experiments, we demonstrate that the hfq mutant is specifically impaired in rpoS translation. We also present evidence that the H-NS protein, which has been shown to affect rpoS translation, acts in the same regulatory pathway as HF-I at a position upstream of HF-I or in conjunction with HF-I. In addition, we show that expression and heat induction of the heat shock sigma factor sigma(32) (encoded by rpoH) is not dependent on HF-I, although rpoH and rpoS are both subject to translational regulation probably mediated by changes in mRNA secondary structure. HF-I is the first factor known to be specifically involved in rpoS translation, and this role is the first cellular function to be identified for this abundant ribosome-associated RNA-binding protein in E. coli.
Từ khóa
Tài liệu tham khảo
1995, A role for the histone-like protein H-NS in growth phase-dependent and osmotic regulation of σs and many σs-dependent genes in Escherichia coli., J. Bacteriol., 177, 3455, 10.1128/jb.177.12.3455-3464.1995
1972, Bacterial proteins required for replication of phage Qβ ribonucleic acid. Purification and properties of host factor I, a ribonucleic acid-binding protein., J. Biol. Chem., 247, 824, 10.1016/S0021-9258(19)45681-0
1993, Synthesis of the stationary-phase sigma factor σs is positively regulated by ppGpp., J. Bacteriol., 175, 7982, 10.1128/jb.175.24.7982-7989.1993
1991, Growth phase-regulated expression of bo1A and morphology of stationary phase Escherichia coli cells is controlled by the novel sigma factor σs (rpoS)., J. Bacteriol., 173, 4474, 10.1128/jb.173.14.4474-4481.1991
1995, Identification of transcriptional start sites and the role of ppGpp in the expression of rpoS, the structural gene for the σs subunit of RNA-polymerase in Escherichia coli., J. Bacteriol., 177, 4676, 10.1128/jb.177.16.4676-4680.1995
1993, KatF (σs) synthesis in Escherichia coli is subject to posttranscriptional regulation., J. Bacteriol., 175, 2150, 10.1128/jb.175.7.2150-2153.1993
1991, The putative σ factor KatF has a central role in development of starvation-mediated general resistance in Escherichia coli., J. Bacteriol., 173, 4188, 10.1128/jb.173.13.4188-4194.1991
1993, The putative σ factor KatF is regulated posttranscriptionally during carbon starvation., J. Bacteriol., 175, 2143, 10.1128/jb.175.7.2143-2149.1993
Miller, J.H. 1972. Experiments in molecular genetics. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY.
1996, The response regulator RssB controls stability of the σs subunit of RNA polymerase in Escherichia coli., EMBO J., 15, 1333, 10.1002/j.1460-2075.1996.tb00475.x
1996, Posttranscriptional osmotic regulation of the σs subunit of RNA polymerase in Escherichia coli., J. Bacteriol., 178, 1607, 10.1128/jb.178.6.1607-1613.1996
1996, Regulation of Escherichia coli starvation sigma factor (σs) by ClpXP protease., J. Bacteriol., 178, 470, 10.1128/jb.178.2.470-476.1996
1976, Site-specific interaction of Qβ host factor and ribosomal protein S1 with Qβ and R17 bacteriophage RNAs., J. Biol. Chem., 251, 1902, 10.1016/S0021-9258(17)33633-5
Silhavy, T.J., M.L. Berman, and L.W. Enquist. 1984. Experiments with gene fusions. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY.
1994, The chromatin-associated protein H-NS alters DNA topology in vitro., EMBO J., 13, 258, 10.1002/j.1460-2075.1994.tb06256.x
1995, Quantitative control of the stationary phase-specific sigma factor, σs, in Escherichia coli: Involvement of the nucleoid protein H-NS., EMBO J., 14, 594, 10.1002/j.1460-2075.1995.tb07035.x