Functional Interactions of Transcription Factor Human GA-binding Protein Subunits

Abstract

The transcription factor human GA-binding protein (hGABP) is composed of two subunits, the Ets-related hGABP␣, which binds to a specific DNA sequence, and either one of two hGABP␣-associated subunits, hGABP␤ or hGABP␥. The DNA-binding protein hGABP␣ cannot affect transcription by itself, but can modify hGABP-dependent transcription in vitro and in vivo in the presence of its associated subunits. In this study, co-transfection assays showed that the ratio of hGABP␤ to hGABP␥ affected transcription from a promoter containing hGABP binding sites. Biochemical analysis showed that they bind to hGABP␣ competitively, indicating that the ratio of hGABP␤ to hGABP␥ is important for hGABP complex formation. Kinetic analysis of the protein-protein interaction using the surface plasmon resonance system showed that hGABP␣ binds to hGABP␤ or hGABP␥ with similar equilibrium constants. Kinetic analysis of the DNA-hGABP interaction showed that the binding of hGABP␥ to hGABP␣ stabilized the interaction of hGABP␣ with its DNA binding site. In addition, the kinetic analysis revealed that this was due to a slower dissociation of the protein complex from the DNA. These results suggest that hGABP␣-associated subunits influence the DNA binding stability of hGABP␣ and regulate hGABP-mediated transcription by competing with each other.

Designed to be stable: Crystal structure of a consensus ankyrin repeat protein

“…Pro 7 initiates the helix and Leu 8 forms hydrophobic contacts to the inner side of the antiparallel helix of the same repeat. Thr 6 forms three H-bonds with the His 9 residue: (i) the backbone CO and (ii) the side-chain OH form H-bonds to the backbone NH of His 9 .…”

“…Target affinities in the low nanomolar range have been reported (6,7). The evolutionary success of members of this protein family originates from their ability to bind to virtually any target protein by simple adaptation of their molecular surface and by displaying highly variable residues throughout the protein.…”

Regulation of Ets function by protein–protein interactions

“…The transcriptional activity of GABPa is dependent upon its heterodimerization with GABPb and the DNA binding a nity of GABPa can be greatly enhanced by this heterodimerization (Gugneja et al, 1995). However, the heterodimer of GABPa with GABPg is unable to active transcription even though GABPg is able to enhance GABPa DNA binding (Sawada et al, 1994;Suzuki et al, 1998). The ratio of GABPb to GABPg may thus control GABP heterodimer-dependent transcription in a tissue speci®c manner (Suzuki et al, 1998).…”

“…However, the heterodimer of GABPa with GABPg is unable to active transcription even though GABPg is able to enhance GABPa DNA binding (Sawada et al, 1994;Suzuki et al, 1998). The ratio of GABPb to GABPg may thus control GABP heterodimer-dependent transcription in a tissue speci®c manner (Suzuki et al, 1998). Homo-dimerization within the Ets family involves the Pointed/HLH domain.…”

A Systems Biology Approach Using Transcriptomic Data Reveals Genes and Pathways in Porcine Skeletal Muscle Affected by Dietary Lysine

“…MORF4L2 (MRGX) is a novel transcription factor and can repress or activate the B-myb promoter [66]. GABPB1 (GA binding protein transcription factor, beta subunit 1) encodes the GA-binding protein transcription factor, beta subunit, which forms a tetrameric complex with the alpha subunit, and influence the DNA binding stability of hGABP alpha and regulate hGABP-mediated transcription [67].…”