Sunday, October 08, 2006

Gene Regulation and E.coli

A news release from the University of Wisconsin-Madison entitled BASIC WORK ON E. COLI IDENTIFIES TWO NEW KEYS TO REGULATION OF BACTERIAL GENE EXPRESSION reveals an important functional relationship between DNA promotor regions and RNA polymerase discovered through research involving the bacterium E.coli. Some italicized paragraphs from the linked article follow along with my comments in block print.


MADISON - The cellular process of transcription, in which the enzyme RNA polymerase constructs chains of RNA from information contained in DNA, depends upon previously underappreciated sections of both the DNA promoter region and RNA polymerase, according to work done with the bacterium E. coli and published today (June 16) in the journal Cell by a team of bacteriologists from the University of Wisconsin-Madison.

This fundamental research about a key step in RNA synthesis has important implications for the study of gene expression in other organisms, and adds to the wealth of knowledge about E. coli contributed by scientists from the UW-Madison.


The article cites more detailed information about a known process involving the enzyme RNA polymerase and a region of DNA known as the promotor.


In his most recent study, Gourse investigated the interaction between RNA polymerase and promoters from the E. coli chromosome. RNA polymerase reads the information in DNA and transcribes it into chains of RNA, which are later translated into proteins. Promoter regions are specific sequences within the DNA chain that tell RNA polymerase when and where to begin transcription, and how much product to make from specific genes.

Gourse's group found that there is a specific region within DNA promoters that makes contact with a highly conserved but previously underappreciated segment of the sigma subunit of RNA polymerase. While the contact with sigma is very strong at promoters for most genes, it is particularly weak at promoters that make ribosomal RNA, which means that other factors like nutritional and environmental signals ultimately regulate the expression of those genes.


The sigma subunit of E.coli RNA polymerase is encoded by a particular gene known as rpoD.

There are five different polypeptide chains in E.coli RNA polymerase suggesting questions as to how the four core polypeptide subunits (alpha (a), beta (b), beta' (b'), and omega (w)) and another subunit known as sigma formed incrementally. The sigma subunit has a transient relationship to the holoenzyme and its function involves identifying the starting point for transcription initiation.

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