Upstream DNA sequences required for tissue-specific expression of the HLA-DR alpha gene.

Abstract

We have used in vitro deletion mutagenesis in combination with DNA transfection to search for cis-acting regulatory elements involved in the tissue-specific expression of a human class H major histocompatibility complex gene. A 140-base-pair 5' flanking fragment that contains the class II box consensus sequences and an octamer sequence (AT-TTGCAT) confers tissue specificity on the promoter of the HLA-DRx gene. Recombinant DNA plasmids containing this DRa gene segment fused to the coding sequence of the bacterial chloramphenicol acetyltransferase gene are expressed at higher levels in human B-cell lines than in human T-cell lines. We have demonstrated that the most 5' of the class II boxes is essential for tissue-specific DRa promoter function. In addition, using an electrophoretic mobility shift assay to identify DNA binding proteins, we have detected binding of nuclear proteins to DNA probes containing the class II boxes and the octamer sequence. A protein that binds to the octamer is present at higher levels in nuclear extracts of B-cell lines than in other cell lines examined. This protein may be important for the tissue-specific expression of the HLA-DRx gene.Class II major histocompatibility complex (MHC) antigens are cell-surface glycoproteins that function in immune cellcell recognition and interaction. These molecules control the level of immune response to certain antigens through their role in the presentation of antigen to class II-restricted, antigen-specific T cells (1). There are at least three human class II antigens, designated DR, DP, and DQ. All class II molecules are composed of two noncovalently associated subunits. The heavy (a) chain is relatively nonpolymorphic, and the light (,B) chain is highly polymorphic.The genes coding for the class II MHC antigens are transcribed in a tissue-specific manner (2). Class II antigens are found primarily on certain cells of the immune system, including B lymphocytes, macrophages, and some activated T cells (3). Class II gene expression is differentially regulated in different cell types and is responsive to multiple regulators (4). For example, class II antigen expression on B cells is modulated by B-cell growth factor (5), whereas that on macrophages is modulated by y-interferon, a-fetoprotein, and prostaglandin E (4). y-Interferon can enhance or induce the expression of class II genes in many different cell types, including some nonlymphoid cells (6).A few studies have employed gene transfer experiments and sequence homology searches to identify cis-acting tran- In this report, we investigate the cis-acting DNA sequences that control tissue-specific expression of class II genes. To do this, we have transfected a set of recombinant plasmids containing 5' promoter deletions of the HLA-DRa gene fused to a bacterial indicator gene into human B-and T-cell lines. We then assayed extracts of transfected cells for DRacontrolled transient expression of the indicator gene. We have also used an electrophoretic mobility shift assay to detect specific bindi...

High mobility group I/Y protein functions as a specific cofactor for Oct-2A: mapping of interaction domains

“…The expression of human class II MHC genes, which is primarily controlled at the level of transcription [12,13], requires the accurate assembly of transcription factor complexes on a number of distinct conserved cis-elements located in their proximal promoter regions [14,15]. In addition to a TATA motif, these include the X, Y, and Z boxes; elements whose sequences as well as stereospecific relationships to each other are highly conserved [16][17][18][19][20][21][22][23][24][25][26]. Several proteins that interact specifically with these cis-acting elements have been described [27][28][29][30][31][32][33][34][35][36][37][38].…”

Two DNA-binding proteins discriminate between the promoters of different members of the major histocompatibility complex class II multigene family.

“…Finally, since MHC class II genes form a multigene family, the mechanisms responsible for the global regulation observed for the entire family of HLA-DR, -DQ, and -DP a-and a-chain genes (8) are of interest. Rare cases of dissociated expression of HLA-DR versus -DQ have also been described elsewhere (13).In transfection experiments, a DNA sequence containing less than 160 base pairs upstream of MHC class II genes is sufficient to confer both B-cell-specific expression (23, 30) and inducibility by gamma interferon (3,28,30). Within this region, three highly conserved sequences are observed in human and mouse class II genes: the X and Y boxes (29) and a heptamer motif, also referred to as the Z or W box (26).…”

MHC class II regulatory factor RFX has a novel DNA-binding domain and a functionally independent dimerization domain

“…These sequences are cis-acting elements playing a central role in class II gene expression (Dom et al 1987b;Sherman et al 1987Sherman et al , 1989Basta et al 1988;Koch et al 1988;Sakurai and Strominger 1988;Tsang et al 1988Tsang et al , 1990Dedrick and Jones 1990). We and others have identified nuclear factors binding specifically to these sequences (Dorn et al 1987a, b;Miwa et al 1987;Reith et al 1988Reith et al , 1989Sherman et al 1989;Dedrick and Jones 1990;Kobr et al 1990;Tsang et al 1990).…”