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Biomedical subjects

D Court

Publications and source records attributed to D Court.

At least 37 records · Page 2Linked to original sources
PubMed1983

Transcription of the sulA gene and repression by LexA.

The Escherichia coli sulA gene product is a highly unstable protein, whose synthesis in response to DNA damage is associated with an inhibition of septation. Genetic evidence as well as sequence information suggests that the sulA gene is part of the E. coli SOS system and is induced after DNA damage. We have constructed a plasmid carrying only the sulA gene; this plasmid is stable only when it contains an amber mutation in the sulA structural gene. Using fragments of this plasmid, we have carried out in vitro transcription experiments and demonstrated one major start site for RNA transcription. We have mapped this initiation point to an adenylate residue 30 nucleotides before the protein start. Purified LexA protein completely abolishes this transcription, in agreement with the prediction made from the genetic and sequence information previously available.

Bacterial Proteins↗
PubMed1983

Deletion analysis of the retroregulatory site for the lambda int gene.

The lambda int gene product, integrase, recombines phage and bacterial DNA at a specific site during the integration step of lysogeny. Regulation of integrase synthesis is complex. (1) Transcription of the gene can occur from either of two promoters. lambda cII protein activates transcription initiation near int at pI. The lambda N protein allows transcription of int from pL. N protein acts by preventing transcription termination at several terminators between pL and int. (2) The expression of integrase is also subject to post-transcriptional regulation by a site, sib, which is located beyond int in the b region of lambda. Expression of int from pL is inhibited by sib, whereas that from pI is not. The negative control of int expression by sib is termed retroregulation. Retroregulation of int is caused, in part, by processing of the pL transcript at the sib site by RNase III of Escherichia coli. The exonuclease, Bal31, was used to generate a set of deletions to define the sib regulatory site. Both sib+ and sib- deletions were sequenced, and it was concluded from this and other work that a dyad symmetry present in the b region, 270 base-pairs from int, was necessary for retroregulation. The RNA structure of this segment is similar to other RNase III-sensitive sites found in E. coli and phage RNAs.

Bacteriophage lambda↗
PubMed1983

High-level expression in Escherichia coli of the carboxy-terminal sequences of the avian myelocytomatosis virus (MC29) v-myc protein.

A plasmid, pJL6, was constructed that contains a unique ClaI site twelve codons beyond the bacteriophage lambda cII gene initiation codon. This site allowed us to fuse the carboxy-terminal sequences of the avian myelocytomatosis virus (MC29) v-myc gene to the amino-terminal portion of the cII gene. Transcription of the hybrid gene is controlled from the phage lambda pL promoter. When this promoter is derepressed, Escherichia coli cells harboring the chimeric plasmid produce a level of cII-myc fusion protein greater than 5% of total cellular protein. Antibodies raised by this protein immunoprecipitate the MC29 gag-myc gene product, P110gag-myc.

Antigen-Antibody Reactions↗
PubMed1983

High-level expression of oncogenes in Escherichia coli.

A plasmid, pJL6, was constructed that contains a unique Cla I site 12 codons beyond the bacteriophage lambda cII gene initiation codon, as well as an adjacent unique Hind III site. These sites allowed us to fuse the sequences from the avian myelocytomatosis virus (MC29) v-myc gene, the avian myeloblastosis virus (AMV) v-myb gene, and the Harvey murine sarcoma virus (Ha-MuSV) v-ras gene to the amino-terminal portion of the cII gene. Transcription of the hybrid genes is controlled from the lambda PL promoter. When this promoter is derepressed, E. coli cells harboring the chimeric plasmid produce levels of fusion proteins that amount to over 5% of total cellular protein. Antibodies raised by the cII-myc fusion protein form an immunoprecipitate with the MC29 gene product, P110gag-myc. The cII-ras fusion protein is precipitated by monoclonal antibodies directed toward the Ha-MSV p21ras, binds GDP, and is capable of autophosphorylation.

Amino Acid Sequence↗
PubMed1982

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

The bacteriophage lambda int gene product, integrase, recombines the phage DNA with the host DNA at specific sites on each to accomplish lysogeny. The int gene is transcribed from two promoters, PL and PI, each regulated positively by lambda proteins. The expression of integrase is also controlled from a site, sib, in the b region of the phage genome. This is a unique regulatory site because it is located distal to the structural gene in relation to the promoters. The expression of int from the PL promoter is inhibited when sib is present. This effect appears to be specific for PL because sib does not cause inhibition of PI-dependent int synthesis. lambda mutants that contain alterations in the site have been isolated. Sequence analyses of the mutations reveal single base changes, spanning 37 base pairs (bp) in the b region, some 240 bp beyond the int gene. Another mutant, hef13, which has a phenotype similar to that of sib, introduces a nucleotide change within the same 37-bp region. The sib and hef mutations cluster within a region of dyad symmetry. Regulation of int synthesis by sib occurs after transcription of the int gene. There is no difference in the rate of PL-promoted int mRNA synthesis in either sib+ or sib- phage infections, yet int mRNA is less stable in the sib+ infection. Because RNase III host mutants are defective in sib regulation, processing of the PL mRNA at sib by this endoribonuclease may cause int mRNA decay and decrease int synthesis.

Bacteriophage lambda↗
PubMed1980

Promoter for the establishment of repressor synthesis in bacteriophage lambda.

Transcription of the lambda repressor gene (cI) is positively regulated by the phage-encoded proteins cII and cIII. We have isolated and characterized the 5'-terminal region of this RNA and shown that it originates at a promoter (pE) located between genes cro and cII. The DNA sequence of this promoter shows little homology to other known promoters. Initiation of transcription from PE is abolished by the cis-dominant mutations cY; these mutations alter the "-10" and "-35" regions of the promoter. We propose that the "-35" region is the site of activation of PE, possibly via the direct interaction of protein cII.

Bacteriophage lambda↗