Evidence for two modes of cooperative DNA binding in vivo that do not involve direct protein-protein interactions.
BACKGROUND
The promoter regions of most eukaryotic genes contain binding sites for more than one transcriptional activator and these activators often bind cooperatively to promoters. The most common type of cooperativity is supported by direct protein-protein interactions. Recent studies have shown that proteins that do not specifically interact with one another can bind cooperatively to chromatin in vitro. probably by the localized destabilization of nucleosome structure by one factor, facilitating binding of another to a nearby site. This mechanism does not require that the transcription factors have activation domains. We have examined whether this phenomenon occurs in vivo.


RESULTS
Unrelated non-interacting proteins can bind DNA cooperatively in yeast cells; this cooperative binding can contribute significantly to transcriptional activation, does not require that both factors have activation domains and is only operative over relatively short distances. In addition to this 'short-range' mechanism, unrelated non-interacting proteins can bind cooperatively to sites separated by hundreds of base pairs, so long as both have potent activation domains.


CONCLUSIONS
Cooperative binding of transcription factors in vivo can occur by several mechanisms, some of which do not require direct protein-protein interactions and which cannot be detected in vitro using naked DNA templates. These findings must be taken into account when evaluating mechanisms for synergistic transcriptional activation.
Vashee
S
S
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712-1096, USA.
Melcher
K
K
Ding
W V
WV
Johnston
S A
SA
Kodadek
T
T
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003574:Cytochrome c Group / Q000235:genetics; D045304:Cytochromes c; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000378:metabolism*; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics / Q000378:metabolism; D007763:Lac Operon / Q000235:genetics; D008957:Models, Genetic; D009875:Operator Regions, Genetic / Q000235:genetics; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000235:genetics*; D000519:alpha-Galactosidase / Q000235:genetics; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D045304:Cytochromes c; D004247:DNA; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D017405:Herpes Simplex Virus Protein Vmw65; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D012697:Serine Endopeptidases; D014157:Transcription Factors; D000519:alpha-Galactosidase; D000099160:LexA Repressor Protein; C014059:CYC1 protein, S cerevisiae; C052130:GAL4 protein, S cerevisiae