A single residue within the homeodomain of the Brn-3 POU family transcription factors determines whether they activate or repress the SNAP-25 promoter.
The closely related POU family transcription factors Brn-3a and Brn-3b differ in their effect on a number of different neuronally expressed promoters such as that of the gene encoding the synaptic vesicle component SNAP-25. Thus Brn-3a activates these promoters whilst Brn-3b represses both their basal activity and their activation by Brn-3a. We show here that alterations of a single amino acid at position 22 in the POU-homeodomain from the isoleucine found in Brn-3b to the valine found at the equivalent position in Brn-3a converts Brn-3b from a repressor to an activator of the SNAP-25 gene promoter. The converse mutation in Brn-3a abolishes its ability to activate the SNAP-25 gene promoter and allows it to repress the basal activity of the promoter and its activation by wild type Brn-3a. This is the first time that a single amino acid change has been shown to convert an activator of a naturally occurring promoter to a repressor and vice versa. These results are discussed in terms of the critical role of position 22 in the POU homeodomain in the protein-protein interactions of POU proteins.
Morris
P J
PJ
Department of Molecular Pathology, University College London Medical School, UK.
Dawson
S J
SJ
Wilson
M C
MC
Latchman
D S
DS
D001711:Biotransformation / Q000502:physiology; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D050809:POU Domain Factors; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000235:genetics*; D050825:Synaptosomal-Associated Protein 25; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050809:POU Domain Factors; C494208:SNAP25 protein, human; D050825:Synaptosomal-Associated Protein 25; D014157:Transcription Factors; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase