Essential regulatory elements for NHE3 gene transcription in renal proximal tubule cells

The objectives of the present study were to identify the cis-elements of the promoter absolutely required for the efficient rat NHE3 gene transcription and to locate positive and negative regulatory elements in the 5’-flanking sequence (5’FS), which might modulate the gene expression in proximal tubules, and to compare this result to those reported for intestinal cell lines. We analyzed the promoter activity of different 5’FS segments of the rat NHE3 gene, in the OKP renal proximal tubule cell line by measuring the activity of the reporter gene luciferase. Because the segment spanning the first 157 bp of 5’FS was the most active it was studied in more detail by sequential deletions, point mutations, and gel shift assays. The essential elements for gene transcription are in the region -85 to -33, where we can identify consensual binding sites for Sp1 and EGR-1, which are relevant to NHE3 gene basal transcription. Although a low level of transcription is still possible when the first 25 bp of the 5’FS are used as promoter, efficient transcription only occurs with 44 bp of 5’FS. There are negative regulatory elements in the segments spanning -1196 to -889 and -467 to -152, and positive enhancers between -889 and -479 bp of 5’FS. Transcription factors in the OKP cell nuclear extract efficiently bound to DNA elements of rat NHE3 promoter as demonstrated by gel shift assays, suggesting a high level of similarity between transcription factors of both species, including Sp1 and EGR-1.

Transformation of the Edible Basidiomycete, Pleurotus ostreatus to Phleomycin Resistance

For transformation of Pleurotus ostreatus, two novel vectors, pPhKM1 and pPhKM2, were constructed, using the regulatory sequences of the P. sajor-caju beta-tubulin gene (TUB1) and the ble gene encoding phleomycin binding protein. pPhKM1 contains ble fused to the TUB1 promoter and the Schizophyllum commune GPD terminator. pPhKM2 contains ble fused to the promoter and terminator regions of P. sajor-caju TUB1. To confirm phleomycin-resistance activity, each vector was cotransformed with pTRura3-2 into the P. ostreatus homokaryotic ura - strain. The transforming DNA was stably integrated into the genomic DNA. Subsequently, phleomycin resistance was conferred on wild-type dikaryotic P. ostreatus by transformation with pPhKM1 or pPhKM2. This transformation system generated stable phleomycin-resistant transformants.

The Escherichia coli antiterminator protein BglG stabilizes the 5'region of the bgl mRNA.

The beta-glucoside utilization (bgl) genes of Escherichia coli are positively regulated by the product of the bglG gene, which functions as an antiterminator by binding to specific sequences present within the bgl mRNA. BglG is inactivated by phosphorylation in the absence of beta-glucosides by BglF, the bgl-specific component of the phosphotransferase system (PTS). Here, we present evidence for an additional function for BglG, namely the stabilization of the 5' end of the bgl mRNA. Half-life measurements of the promoter-proximal region of the bgl mRNA indicate a five fold enhancement of stability in the presence of active (unphosphorylated) BglG. This enhancement is lost when the binding of BglG to mRNA is prevented by deletion of the binding site. Interestingly, stabilization by BglG does not extend to downstream sequences. The enhanced stability of the upstream sequences suggest that BglG remains bound to its target on the mRNA even after the downstream sequences have been degraded. Implications of these observations for the mechanism of positive regulation of the operon by BglG are discussed.

Characterization and Sequence Analysis of Helicobacter pylori Cryptic Plasmid (pHP489)

The DNA sequence of a plasmid named pHP489 of Helicobacter pylori strain 489 was determined and analyzed to characterize its replication apparatus. The pHP489 plasmid consisted of 1,222 bp and had an overall G+C content of 33.1%. An ORF was predicted to encode the putative protein of 239 amino acid residues (28 kDa). A putative ribosomal binding site and a potential terminator sequence are located upstream and downstream of the ORF, respectively. However, the consensus sequence for a promoter in upstream of ORF was not found. A potential dna A box was found at 317 nt upstream of a start codon and followed by two-57 bp directed repeats and an inverted repeat. The DNA homology was found in the regions of less than 90 bp among pHPK255, pHPM180, and pHel1 of other H. pylori plasmids and Mycoplasma mycoides plasmids. pHP489K that was produced by pHP489 sequence and C. jejuni derived aph(3')-III, was transformed to various H. pylori isolates and were stably maintained in the H. pylori host without the addition of selective antibiotics for the 30-times subcultues. The plasmic vector, in which the ORF region of pHP489 DNA was deleted, could be transformed into H. pylori. However, the plasmid vector, whose the direct repeats region of pHP489 DNA was deleted, failed to be transformed. The direct repeats region of pHP489 DNA was confirmed to be bound with cytosolic factors of H. pylori. These results showed that the direct repeats region of pHP489 DNA is an essential apparatus by which the plasmid could be replicacted in H. pylori. And pHP489 plasmid was supposed to be replicated by host factors rather than plasmic-encoded factors.