Gene Information
Gene Symbol
Entrez Gene ID
Gene Name
Major histocompatibility complex, class II, DQ alpha 1
Chromosomal Location
HLA-DQA1 belongs to the HLA class II alpha chain paralogues. The class II molecule is a heterodimer consisting of an alpha (DQA) and a beta chain (DQB), both anchored in the membrane. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B Lymphocytes, dendritic cells, macrophages). The alpha chain is approximately 33-35 kDa. It is encoded by 5 exons; exon 1 encodes the leader peptide, exons 2 and 3 encode the two extracellular domains, and exon 4 encodes the transmembrane domain and the cytoplasmic tail. Within the DQ molecule both the alpha chain and the beta chain contain the polymorphisms specifying the peptide binding specificities, resulting in up to four different molecules. Typing for these polymorphisms is routinely done for bone marrow transplantation. [provided by RefSeq, Jul 2008]
RefSeq DNA
RefSeq mRNA

Gene Ontology (GO)

GO ID Ontology Function Evidence Reference
GO:0006955 Biological process Immune response NAS 3584986, 6415485
GO:0005887 Cellular component Integral component of plasma membrane NAS 3584986, 6415485
GO:0016020 Cellular component Membrane HDA 19946888
GO:0042613 Cellular component MHC class II protein complex ISS 20356827
GO:0005515 Molecular function Protein binding IPI 14769912, 17629515, 29997244
Protein Information
Protein Name
HLA class II histocompatibility antigen, DQ alpha 1 chain, DC-1 alpha chain, DC-alpha, HLA-DCA, MHC HLA-DQ alpha, MHC class II DQ alpha chain, MHC class II DQA1, MHC class II HLA-DQ-alpha-1, MHC class II antigen DQA1, truncated MHC class II antigen
Binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accommodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Exogenous antigens that have been endocytosed by the APC are thus readily available for presentation via MHC II molecules, and for this reason this antigen presentation pathway is usually referred to as exogenous. As membrane proteins on their way to degradation in lysosomes as part of their normal turn-over are also contained in the endosomal/lysosomal compartments, exogenous antigens must compete with those derived from endogenous components. Autophagy is also a source of endogenous peptides, autophagosomes constitutively fuse with MHC class II loading compartments. In addition to APCs, other cells of the gastrointestinal tract, such as epithelial cells, express MHC class II molecules and CD74 and act as APCs, which is an unusual trait of the GI tract. To produce a MHC class II molecule that presents an antigen, three MHC class II molecules (heterodimers of an alpha and a beta chain) associate with a CD74 trimer in the ER to form a heterononamer. Soon after the entry of this complex into the endosomal/lysosomal system where antigen processing occurs, CD74 undergoes a sequential degradation by various proteases, including CTSS and CTSL, leaving a small fragment termed CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM via direct binding to the alpha-beta-CLIP complex so that CLIP is released. HLA-DM stabilizes MHC class II molecules until primary high affinity antigenic peptides are bound. The MHC II molecule bound to a peptide is then transported to the cell membrane surface. In B-cells, the interaction between HLA-DM and MHC class II molecules is regulated by HLA-DO. Primary dendritic cells (DCs) also to express HLA-DO. Lysosomal microenvironment has been implicated in the regulation of antigen loading into MHC II molecules, increased acidification produces increased proteolysis and efficient peptide loading
Refseq Proteins

Cell adhesion molecules (CAMs)
Antigen processing and presentation
Hematopoietic cell lineage
Th1 and Th2 cell differentiation
Th17 cell differentiation
Intestinal immune network for IgA production
Type I diabetes mellitus
Staphylococcus aureus infection
Influenza A
Human T-cell leukemia virus 1 infection
Herpes simplex virus 1 infection
Epstein-Barr virus infection
Autoimmune thyroid disease
Inflammatory bowel disease (IBD)
Systemic lupus erythematosus
Rheumatoid arthritis
Allograft rejection
Graft-versus-host disease
Viral myocarditis


Downstream TCR signaling
Phosphorylation of CD3 and TCR zeta chains
Translocation of ZAP-70 to Immunological synapse
Generation of second messenger molecules
MHC class II antigen presentation
PD-1 signaling
Interferon gamma signaling

ENSP00000369017 P51460
    View interactions

Associated Diseases

Disease groupDisease NameReferences
Digestive System Diseases
Inflammatory Bowel Diseases
Esophageal Achalasia
Ear Or Mastoid Diseases
Meniere Disease
PMID: 1471701

Increased risk for polycystic ovary syndrome associated with human leukocyte antigen DQA1*0501.

Ober C, Weil S, Steck T, Billstrand C, Levrant S, Barnes R
Department of Obstetrics and Gynecology, Chicago Lying-In Hospital, University of Chicago, IL 60637.
Am J Obstet Gynecol. 1992 Dec;167(6):1803-6. doi: 10.1016/0002-9378(92)91778-9.

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