HLA-DQB1
Encyclopedia
Major histocompatibility complex, class II, DQ beta 1, also known as HLA-DQB1, is a human gene
and also denotes the genetic locus
that contains this gene. The protein
encoded by this gene is one of two proteins that are required to form the DQ heterodimer
, a cell surface receptor
essential to the function of the immune system
.
beta chain paralogues. This 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).
s. Exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular protein domain
s, exon 4 encodes the transmembrane
domain, and exon 5 encodes the cytoplasm
ic tail. Within the DQ molecule, both the alpha chain and the beta chain contain the polymorphism
s specifying the peptide binding specificities, resulting in up to 4 different molecules. Typing for these polymorphisms is routinely done for bone marrow transplantation.
s of HLA-DQB1 are associated with an increased risk of developing type 1 diabetes
. The locus also has the genetic name IDDM1 as it is the highest genetic risk for type 1 diabetes. Again the DQB1*0201 and DQB1*0302 alleles, particularly the phenotype DQB1*0201/*0302 has a high risk of late onset type 1 diabetes. The risk is partially shared with the HLA-DR locus (DR3 and DR4 serotypes).
coeliac disease
. Homozygotes of DQB1*0201 have a higher risk of developing the coeliac disease, relative to any other genetic locus.
.
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
and also denotes the genetic locus
Locus (genetics)
In the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...
that contains this gene. The protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
encoded by this gene is one of two proteins that are required to form the DQ heterodimer
HLA-DQ
HLA-DQ is a cell surface receptor type protein found on antigen presenting cells. DQ is an αβ heterodimer of the MHC Class II type. The α and β chains are encoded by HLA-DQA1 and HLA-DQB1, respectively. These two loci are adjacent to each other on chromosome 6p21.3. Both the α-chain and β-chain...
, a cell surface receptor
Immune receptor
An immune receptor is a receptor, usually on a cell membrane, which binds to a substance and causes a response in the immune system.-Types:...
essential to the function of the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
.
Function
HLA-DQB1 belongs to the HLA class IIMHC class II
MHC Class II molecules are found only on a few specialized cell types, including macrophages, dendritic cells and B cells, all of which are professional antigen-presenting cells ....
beta chain paralogues. This 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).
Gene structure and polymorphisms
The beta chain is approximately 26-28 kDa and it contains 5 exonExon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
s. Exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular protein domain
Protein domain
A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...
s, exon 4 encodes the transmembrane
Transmembrane protein
A transmembrane protein is a protein that goes from one side of a membrane through to the other side of the membrane. Many TPs function as gateways or "loading docks" to deny or permit the transport of specific substances across the biological membrane, to get into the cell, or out of the cell as...
domain, and exon 5 encodes the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
ic tail. Within the DQ molecule, both the alpha chain and the beta chain contain the polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
s specifying the peptide binding specificities, resulting in up to 4 different molecules. Typing for these polymorphisms is routinely done for bone marrow transplantation.
Diabetes
Several alleleAllele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s of HLA-DQB1 are associated with an increased risk of developing type 1 diabetes
Diabetes mellitus type 1
Diabetes mellitus type 1 is a form of diabetes mellitus that results from autoimmune destruction of insulin-producing beta cells of the pancreas. The subsequent lack of insulin leads to increased blood and urine glucose...
. The locus also has the genetic name IDDM1 as it is the highest genetic risk for type 1 diabetes. Again the DQB1*0201 and DQB1*0302 alleles, particularly the phenotype DQB1*0201/*0302 has a high risk of late onset type 1 diabetes. The risk is partially shared with the HLA-DR locus (DR3 and DR4 serotypes).
Coeliac disease
Celiac1 is a genetic name for DQB1, the HLA DQB1*0201, *0202, and *0302 encode genes that mediate the autoimmuneAutoimmune disease
Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. In other words, the body actually attacks its own cells. The immune system mistakes some part of the body as a pathogen and attacks it. This may be restricted to...
coeliac disease
Coeliac disease
Coeliac disease , is an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy onward...
. Homozygotes of DQB1*0201 have a higher risk of developing the coeliac disease, relative to any other genetic locus.
Multiple sclerosis
Certain HLA-DQB1 alleles are also linked to a modest increased risk of multiple sclerosisMultiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
.
Alleles
| Serotype | DQB1 allele |
|---|---|
| DQ2 HLA-DQ2 HLA-DQ2 is a serotype group within HLA-DQ serotyping system. The serotype is determined by the antibody recognition of β2 subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ2 are encoded by the HLA-DQB1*02 allele group. This group currently contains two common alleles,... |
*0201 |
| *0202 | |
| *0203 | |
| DQ4 HLA-DQ4 HLA-DQ4 is a serotype subgroup within HLA-DQ serotypes. The serotype is determined by the antibody recognition of β4 subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ4 are encoded by the HLA-DQB1*04 allele group. This group currently contains 2 common alleles, DQB1*0401... |
*0401 |
| *0402 | |
| *0501 | |
| *0502 | |
| *0503 | |
| *0504 | |
| *0601 | |
| *0602 | |
| *0603 | |
| *0604 | |
| *0605 | |
| *0609 | |
| DQ7 HLA-DQ7 HLA-DQ7 is an HLA-DQ serotype that recognizes the common HLA DRB1*0301 and the less common HLA DRB1*0304 gene products. DQ7 is a form of 'split antigen' of the broad antigen group DQ3 which also contains DQ8 and DQ9.... |
*0301 |
| *0304 | |
| DQ8 HLA-DQ8 HLA-DQ8 is a human leukocyte antigen serotype within the HLA-DQ serotype group. DQ8 is a split antigen of the DQ3 broad antigen. DQ8 is determined by the antibody recognition of β8 and this generally detects the gene product of DQB1*0302.... |
*0302 |
| *0305 | |
| DQ9 HLA-DQ9 HLA-DQ9 is a human leukocyte antigen serotype within the HLA-DQ serotype group. DQ8 is a split antigen of the DQ3 broad antigen. DQ8 is determined by the antibody recognition of β9 and this generally detects the gene product of DQB1*0303.-Serology:... |
*0303 |