Searching the yeast Saccharomyces cerevisiae genome, researchers found approximately 4,000 DNA sites with a sequence which could potentially bind the yeast transcription factor GAL4.  GAL4 activates the transcription of galactose genes.  Yet there are only 10 GAL4-binding sites which control the genes necessary for galactose metabolism.  The GAL4 binding sequence is CGGAT#AGAAGC*GCCG, where # is T, C or G, and * is C or T. In one chromatin immunoprecipitation experiment (ChIP), yeast growing on galactose were lysed, and subjected to cross-linking reagents which cross-linked transcription factors and activators to DNA. Next the DNA was sheared into small fragments, and antibodies to GAL4 were added.  These antibodies coprecipitated the GAL4 and the DNA it was cross-linked to.  The cross-linking was then chemically reversed, and the DNA was isolated, cloned into a library of plasmids and sequenced.  Results showed that only 10 different DNA sequences had GAL4 bound.  Since the GAL4-binding sequence has little variation, the surrounding DNA sequences were used to judge if the site was distinct. Name and give a short explanation of four possible eukaryotic gene control strategies would allow GAL4 to bind to the 10 sites and would prevent its binding to the 3,990 other sites.

Searching the yeast Saccharomyces cerevisiae genome, researchers found approximately 4,000 DNA sites with a sequence which could potentially bind the yeast transcription factor GAL4.  GAL4 activates the transcription of galactose genes.  Yet there are only 10 GAL4-binding sites which control the genes necessary for galactose metabolism.  The GAL4 binding sequence is CGGAT#AGAAGC*GCCG, where # is T, C or G, and * is C or T.

In one chromatin immunoprecipitation experiment (ChIP), yeast growing on galactose were lysed, and subjected to cross-linking reagents which cross-linked transcription factors and activators to DNA. Next the DNA was sheared into small fragments, and antibodies to GAL4 were added.  These antibodies coprecipitated the GAL4 and the DNA it was cross-linked to.  The cross-linking was then chemically reversed, and the DNA was isolated, cloned into a library of plasmids and sequenced.  Results showed that only 10 different DNA sequences had GAL4 bound.  Since the GAL4-binding sequence has little variation, the surrounding DNA sequences were used to judge if the site was distinct.

Name and give a short explanation of four possible eukaryotic gene control strategies would allow GAL4 to bind to the 10 sites and would prevent its binding to the 3,990 other sites.