|
|
|
|
|
|
Evidence for HrpXo-Dependent Expression of Type II Secretory Proteins in Xanthomonas oryzae pv. oryzae. Ayako Furutani, 2004.Xanthomonas oryzae pv . oryzae is a causal agent of bacterial leaf blight of rice . Recently, an efficient hrp-inducing medium, XOM2, was established for this bacterium . In this medium, more than 10 proteins were secreted from the wild-type strain ofX . oryzae pv . oryzae . Many of these proteins disappeared or decreased in amount in culture on XOM2 when incubated with thestrain that has a mutation in the hrp regulatory gene . Interestingly, the secretory protein profile of a mutant lacking a type III secretion system [TTSS], components of which are encoded byhrp genes, was similar to that of the wild-type strain exceptthat a few proteins had disappeared . This finding suggests thatmany HrpXo-dependent secretory proteins are secreted via systemsother than the TTSS . By isolating mutant strains lacking a typeII secretion system, we examined this hypothesis . As expected,many of the HrpXo-dependent secretory proteins disappeared ordecreased when the mutant was cultured in XOM2 . By determiningthe N-terminal amino acid sequence, we identified one of thetype II secretory proteins as a cysteine protease homolog, CysP2.Nucleotide sequence analysis revealed that cysP2 has an imperfectplant-inducible-promoter box, a consensus sequence which HrpXoregulons possess in the promoter region, and a deduced signalpeptide sequence at the N terminus . By reverse transcription-PCRanalysis and examination of the expression of CysP2 by usinga plasmid harboring a cysP2::gus fusion gene, HrpXo-dependentexpression of CysP2 was confirmed . Here, we reveal that thehrp regulatory gene hrpXo is also involved in the expressionof not only hrp genes and type III secretory proteins but alsosome type II secretory proteins. Transcriptional Analysis of the groES-groEL1, groEL2, and dnaK genes in Corynebacterium glutamicum: Characterization of Heat Shock-Induced Promoters. Carlos Barreiro, 2004.The appropriate conditions to switch on the heat shock promoters in Corynebacterium glutamicum were defined by Northern blot analysis . Transcriptional patterns were characterized for the groEL2 gene and the groES-groEL1 and dnaK operons . Transcriptional start points of these genes were determined by primer extension analysis, allowing the identification of CIRCE and HAIR boxes close to the –10 and –35 regions of the promoters . The presence of both CIRCE and HAIR sequences within a single promoter (P-groEL2) in bacteria is described for the first time . In addition, the dnaK promoter showed –10 and –35 sequences similar to those recognized by SigH of Mycobacterium and SigR of Streptomyces close to a second transcription start region with –10 and –35 boxes typical of promoters for housekeeping genes . Multiple Promoter Inversions Generate Surface Antigenic Variation in Mycoplasma penetrans. Atsuko Horino, 2003.Mycoplasma penetrans is a newly identified species of the genus Mycoplasma . It was first isolated from a urine sample from a human immunodeficiency virus (HIV)-infected patient . M . penetrans changes its surface antigen profile with high frequency . The changes originate from ON  OFF phase variations of the P35 family of surface membrane lipoproteins . The P35 family lipoproteins are major antigens recognized by the human immune system during M . penetrans infection and are encoded by the mpl genes . Phase variations of P35 family lipoproteins occur at the transcriptional level of mpl genes; however, the precise genetic mechanisms are unknown . In this study, the molecular mechanisms of surface antigen profile change in M . penetrans were investigated . The focus was on the 46-kDa protein that is present in M . penetrans strain HF-2 but not in the type strain, GTU . The 46-kDa protein was the product of a previously reported mpl gene, pepIMP13, with an amino-terminal sequence identical to that of the P35 family lipoproteins . Nucleotide sequencing analysis of the pepIMP13 gene region revealed that the promoter-containing 135-bp DNA of this gene had the structure of an invertible element that functioned as a switch for gene expression . In addition, all of the mpl genes of M . penetrans HF-2 were identified using the whole-genome sequence data that has recently become available for this bacterium . There are at least 38 mpl genes in the M . penetrans HF-2 genome . Interestingly, most of these mpl genes possess invertible promoter-like sequences, similar to those of the pepIMP13 gene promoter . A model for the generation of surface antigenic variation by multiple promoter inversions is proposed .
rRNA Antitermination Functions with Heat Shock Promoters. Hyuk Kyu Seoh, 2003.Transcription antitermination in the rRNA operons of Escherichia coli requires a unique nucleic acid sequence that serves as a signal for modification of the elongating RNA polymerase, making it resistant to Rho-dependent termination . We examined the antitermination ability of RNA polymerase elongation complexes that had initiated at three different heat shock promoters, dnaK, groE, and clpB, and then transcribed the antitermination sequence to read through a Rho-dependent terminator . Terminator bypass comparable to that seen with  70 promoters was obtained . Lack of or inversion of the sequence abolished terminator readthrough . We conclude that RNA polymerase that uses
32 to initiate transcription can adopt a conformation similar to that of
70-containing RNA polymerase, enabling it to interact with auxiliary modifying proteins and bypass Rho-dependent terminators .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
