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Welcome to the Linn Lab


Dr. Tom Linn (BSc Minnesota ; PhD Harvard)
Associate Professor

Office: Dental Sciences Building , Room 3013C

Phone: ( 519) 661-3426

Fax: 519 661-3499

Email: tlinn@uwo.ca

How does a cell regulate its total transcriptional ability and how is this related to the general control of cell growth? This laboratory is pursuing these questions by examining the regulation of synthesis of RNA polymerase in E. coli . This single transcriptase in E. coli is a multimeric enzyme whose subunit genes map at different regions of the chromosome, yet the subunits are synthesized in stoichiometric amounts.

We are concentrating our efforts on the regulation of the two major polymerase subunits, ß and ß', whose genes form a single operon. These two genes are part of a complex transcriptional unit that also contains four upstream ribosomal protein genes. This demonstrates an intimate regulation of the cell's transcriptional and translational machineries. However under various growth conditions the individual proteins are synthesized at different rates. Therefore, even though these genes form a single operon there must be additional control mechanisms which allow for their differential expression. These regulatory features include two promoters, a transcriptional attenuator and feedback regulation of translation.

The operon's regulatory sites and the molecular mechanism of these controls are being examined by a combination of molecular biological approaches including: recombinant DNA techniques, gene fusions using both ß-galactosidase and luciferase as reporters, RNA-DNA hybridization, in vitro transcription, bacterial genetics, RNA structure probing and in vitro mutagenesis.


Dykxhoorn, D.M., St. Pierre, R. and Linn, T. 1996. Synthesis of the ß and ß' subunits of Escherichia coli RNA polymerase is autogenously regulated in vivo by both transcriptional and translational mechanisms. Molecular Microbiology 19, 483-493 .

St. Pierre, R. and Linn, T. 1996. A refined system for the in vitro construction of single-copy transcriptional or translational fusions to lacZ . Gene 169, 65-68 .

Dykxhoorn, D.M., St. Pierre, R. and Linn, T. 1996. A set of compatible tac promoter expression vectors. Gene 177: 133-136

Steward, K.L., St. Pierre, R. and Linn, T. 1997. Transcription-frequency-dependent modulation of an attenuator in a ribosomal protein-RNA polymerase operon requires an upstream site. Microbiology 143: 3501-3511 .

Dykxhoorn, D.M., St. Pierre, R. Van Ham, O. and Linn, T. 1997. An efficient protocol for linker scanning mutagenesis: analysis of the translational regulation of an Escherichia coli RNA polymerase subunit gene. Nucleic Acids Res. 25: 4209-4218 .




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