Biomedical subjects

L E Post

Publications and source records attributed to L E Post.

41 records · Page 3Linked to original sources

PubMed1979

Nucleotide sequence of the intercistronic region preceding the gene for RNA polymerase subunit alpha in Escherichia coli.

The gene for RNA polymerase subunit alpha is a co-transcribed with several ribosomal protein genes (Jaskunas, S.R., Burgess, R.R., and Nomura, M. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 5036-5040). The DNA sequence whicch codes for the COOH-terminal amino acids of S4 and the NH2-terminal amino acids of alpha, and the 25 nucleotide intercistronic sequence have been determined. This short distance supports the idea that some post-transcriptional regulation determines the differential synthesis of alpha and ribosomal proteins.

Amino Acid Sequence↗

PubMed1979

Isolation and characterization of stable hybrid mRNA molecules transcribed from ribosomal protein promoters in E. coli.

The promoters from the str and spc operons of ribosomal proteins from E. coli were inserted into the Hind II cleavage site of mini-Col E1 (pVH51) plasmid. For both promoters, strains with the hybrid plasmid accumulated a small RNA species not present in strains carrying the vector. These RNAs were analyzed by RNA sequencing techniques and compared to DNA sequences. In both cases, synthesis of the new RNA species is initiated by the cloned r protein promoter at the site predicted by previous in vitro experiments. The RNAs extend across the Hind II site used for cloning and terminate specifically in the vector sequences. The termination site was localized to six consecutive thymine nucleotides preceded by a sequence with dyad symmetry. We found that the RNA from the str promoter was 205 (+/- 3) nucleotides long and that from the spc promoter was 177 (+/- 3) nucleotides long. These "hybrid mRNAs" are much more stable than ordinary mRNA. The str hybrid mRNA has a half-life of about 8 min, and the spc hybrid mRNA has a half-life of about 18 min at 37 degrees C. These hybrid mRNAs provide an in vivo system with which to examine directly the discrete transcription products from ribosomal protein promoters, and to study promoter function and mRNA metabolism in vivo.

Bacterial Proteins↗

PubMed1979

Nucleotide sequence of the ribosomal protein gene cluster adjacent to the gene for RNA polymerase subunit beta in Escherichia coli.

The 3072-nucleotide-long sequence of a segment from the 88-min region of the Escherichia coli chromosome has been determined. The sequence covers the genes for ribosomal proteins L11 (rplK), LI (rplA), L10 (rplJ), and L7/L12 ((rplL), and the 5' end of the gene for the beta subunit of RNA polymerase (rpoB), along with the presumed regulatory regions for these genes. The probable locations of the promoter for the first two genes (the L11 operon) and the promoter for the latter three genes (the proximal part of the beta operon) have been identified. We have also found that the four ribosomal protein genes preferentially use codons that are recognized efficiently by the most abundant tRNA species. These and other features of the sequence results are discussed in relation to available information obtained from both in vitro and in vivo experiments on the expression of these ribosomal and RNA polymerase subunit genes.

Base Sequence↗

PubMed1978

DNA sequences of promoter regions for the str and spc ribosomal protein operons in E. coli.

The DNA sequences have been determined for promoter regions of two ribosomal protein operons in E. coli, the str operon and the spc operon. The site of in vitro transcription initiation within each of these promoter regions has been determined. The start site of the str operon occurs 69 bases upstream from the initiation codon of the S12 gene. The start site of the spc operon occurs 72 bases upstream from the L14 gene, and only 91 bases downstream from the termination codon of the S17 gene (which is in the preceding S10 operon). Both promoters are similar to other sequenced promoters in that they each have an identifiable "Pribnow box" sequence 5 bases upstream from the transcription start site. The spc promoter has a long sequence of 2 fold symmetry centered within the Pribnow box; the str promoter has a shorter but similar symmetry. At positions -69 through -40 in the spc operon, another long region of symmetry is present which may be the termination signal of the preceding S10 operon. Extensive sequence similarity between the str and spc promoter regions is found downstream from the Pribnow box-that is, in a transcribed region preceding the translation start sites.

Bacterial Proteins↗

PubMed1978

Isolation and characterization of a promoter mutant in the str ribosomal protein operon in E. coli.

The lambda fus3 transducing phage carries several operons for ribosomal proteins of E. coli, including the str operon. A mutant transducing phage with a promoter mutation in this operon has been isolated. This mutant shows reduced stimulation of synthesis of proteins encoded by the operon, S12, S7, and elongation factors G and Tu, in ultraviolet-irradiated cells. This mutation also abolishes in vitro transcription from the str promoter. The DNA sequence of the mutant promoter shows that it is a point mutation 6 bases upstream from the in vitro transcription start site, changing the "Pribnow box" sequence from TAAAATT to TAAAACT. These results indicate that the site altered by the mutation, which is in the region just preceding the transcription start site, is important for the expression of the str operon.

Bacterial Proteins↗