High mobility group I/Y protein functions as a specific cofactor for Oct-2A: mapping of interaction domains.
The octamer motif (ATTTGCAT) present in several eukaryotic promoters and enhancers is now known to influence the transcription of several genes by interacting with members of a broad family of homeodomain proteins. The promoter of the human class II MHC gene HLA-DRA contains a conserved octamer element that can bind (among other proteins) the transcription factor Oct-2A and the high mobility group proteins (HMG) I/Y. We have previously determined that HMG I(Y) and Oct-2A cooperatively activate HLA-DRA gene expression, most likely due to the ability of HMG I(Y) to selectively recruit Oct-2A to the octamer motif. In this report, we present results of our investigations of the mechanisms of cooperative transactivation of HLA-DRA transcription by Oct-2A and HMG I(Y). We show that both the amino- and the carboxy-terminal domains of Oct-2A are required for HLA-DRA transactivation. Experiments using domain-swap chimeras of the Oct-1 and Oct-2A polypeptides indicate that cooperative activation of the DRA gene by HMG I(Y) and Oct-2A requires the carboxy-terminal domain (CTD) of Oct-2A. However, HMG I(Y) physically interacts with the conserved POU domains of both Oct-1 and Oct-2A. We therefore postulate that the nature of the CTD attached to the POU homeodomain influences the outcome of interaction with HMG I(Y). These studies support the view that HMG I(Y) is an important cofactor for HLA-DRA gene activation by Oct-2A and provide insights into its mechanism of action.
Abdulkadir
S A
SA
Laboratory of Molecular Immunology, The Schepens Eye Research Institute & Committee on Immunology, Harvard Medical School, Boston, Massachusetts 02114, USA.
Casolaro
V
V
Tai
A K
AK
Thanos
D
D
Ono
S J
SJ
D001665:Binding Sites; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006684:HLA-DR Antigens / Q000235:genetics*; D059805:HLA-DR alpha-Chains; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000502:physiology*; D051863:Host Cell Factor C1; D006801:Humans; D019169:Jurkat Cells; D046911:Macromolecular Substances; D008958:Models, Molecular; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D050809:POU Domain Factors; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
D002843:Chromatin; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D006609:High Mobility Group Proteins; D051863:Host Cell Factor C1; D046911:Macromolecular Substances; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D050809:POU Domain Factors; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025741:HMGA1a Protein