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GAL1 repression by glucose

Mark Johnston mj at SEQUENCER.WUSTL.EDU
Mon Nov 20 18:55:53 EST 1995


On 20 Nov., 1995 Colin MacDiarmid wrote:

> I have made a
>construct by amplifying an ORF and cloning into a Gal1-expression vector
>The gene works fine on galactose, but appears to be still expressed on
>glucose plates.
>What is the basal level of expression of the Gal1 promoter on glucose?  I
>had read
>it was very tightly regulated.

Hi Colin and other buddies,

        The GAL1 promoter is tightly regulated:  it's about 1000-fold
repressed by glucose
(see MCB 14:3834, and references therein).  However, there must be some
very low level of expression even on glucose, since I have heard of several
cases where essential genes expessed from the GAL1 promoter still
complement a null mutant for growth on glucose.  The interpretation is that
these gene products are required at extremely low levels, so I predict that
only a very low level of expresison of Colin's gene is required to complement
his phenotype.

        I can't give off the top of my head references to this, but
I'll bet you'll find out about several of these cases from others in the
discussion group.

Bye,



        Mark Johnston
        Department of Genetics Box 8232
        Washington University Medical School
        4566 Scott Ave.
        St. Louis, MO  63110
        TEL:     314-362-2735
        FAX:   314-362-2985 or 7855
        E-mail:  mj at sequencer.wustl.edu





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