Gary R. Janssen
Professor of Microbiology
Research in our laboratory is focussed in three areas: 1) translation of leaderless mRNA in bacteria, 2) analysis of antibiotic resistance genes, and 3) regulatory effects of phosphate on primary and secondary metabolism in Streptomyces.
The majority of prokaryotic mRNAs contain an untranslated leader region, located 5' to the coding sequence, that is believed to function in the association of mRNA that naturally lack upstream leader sequences but continue to be translated. Among the questions we want to ask are the following: What are the nucleotide or structural features that determine the translational efficiency of leaderless mRNA? Do leaderless mRNAs translated by all ribosomes or by a specialized subpopulation of ribosomes? Is the translation of leaderless mRNA influenced by physiological conditions? In addition, we have demonstrated that conventionally leadered mRNA continue to be translated after removal of their upstream leader regions; efforts are under way to identify possible advantages of the leadered or unleadered state for mRNA.
In antibiotic-producing streptomycetes, the antibiotic resistance genes are physically linked to antibiotic production genes. In order to prevent suicide, expression of resistance must precede antibiotic production. We are using a molecular biological approach to the study of resistance gene regulation and the relationship between expression of resistance gene(s) and antibiotic production.
Antibiotic production and secondary metabolism in Streptomyces are regulated, in part, by the extracellular levels of phosphate. We have isolated mutants that are impaired in the normal regulation of antibiotic production by phosphate. These mutations are being mapped to the Streptomyces chromosome and a gene bank of Streptomyces DNA is being used to isolate the genes involved in phosphate regulation of primary and secondary metabolism.
- O'Donnell, S. and G.R. Janssen. 2002. Leaderless mRNAs bind 70S ribosomes more strongly than 30S subunits in Escherichia coli J. Bacteriol. 184:6730-6733.
- O'Donnell, S. and G.R. Janssen. 2001. The initiation codon affects ribosome binding and translational efficiency in Escherichia coli of cI mRNA with or without the 5' untranslated leader. J. Bacteriol. 183:1277-1283.
- Martin-Farmer, J. and G.R. Janssen. 1999. A downstream CA repeat sequence increases translation from leadered and unleadered mRNA in Escherichia coli. Mol. Microbiol. 31:1025-1038.
- VanEtten, W. and G.R. Janssen. 1998. An AUG initiation codon, not codon-anticodon complementarity, is required for the translation of unleadered mRNA in Escherichi coli. Mol. Microbiol. 27:987-1001.
- Wu, C.J., and G.R. Janssen. 1997. Expression of a streptomycete leaderless mRNA encoding chloramphenicol acetyltransferase in Escherichia coli. J. Bacteriol. 179:6824-6830.