Tightest promoter repression ?

Keith Robison robison1 at husc10.harvard.edu
Mon Oct 12 22:33:48 EST 1992


jgraham at bronze.ucs.indiana.edu (the End) writes:

>I need to find a promoter which is very tigthly regulated for use in reducing
>the expression of downstream Lac sequence to a very low level.

I don't have personal experience with it, but you should check out
Studier's work with a T7 promoter -- T7 RNA polymerase -- T7 lysozyme
-- lac repressor system.  T7 lysozyme is an inhibitor of T7 RNA polymerase
(1).  The deluxe system is therefore:

	(a) T7 lysozyme & lac repressor under constituitive promoters
	(b) T7 RNAP under an inducible promoter
	(c) your gene driven by a T7 promoter, with a lac operator
	    between the two.

The basal lysozyme expression kills the basal T7 RNAP expression (2), 
and the lac repressor provides the insurance (3).  The system works well
enough to allow T7 RNAP to be cloned behind a T7 promoter --
a combination which is ordinarily lethal (4).

	1. Cell (1987) 49:221-227
	2. J.Mol.Bio. (1991) 219:37-44
	3. J.Mol.Bio. (1991) 219:45-59
	4. J.Mol.Bio. (1991) 219:61-68


Keith Robison
Harvard University
Department of Cellular & Developmental Biology
Department of Genetics / HHMI

robison at ribo.harvard.edu 



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