HLA-DQA1
Encyclopedia
Major histocompatibility complex, class II, DQ alpha 1, also known as HLA-DQA1, is a human gene
present on short arm of chromosome 6 (6p21.3) and also denotes the genetic locus
which 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
.
alpha 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, exon
s 2 and 3 encode the two extracellular protein domain
s, exon 4 encodes the transmembrane
domain and 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.
) and HLA-DQB1*06 (DQ6
). DQ1 is a serotype, rare among serotypes for human class II antigens, in that the antibodies to DQ1 react to the alpha chain of HLA DQ, these DQA1 allele gene products.
{| class = "wikitable"
|+ HLA-DQA1 alleles
! DQA1 || colspan = 6 | linked DQB1 allele
|-
| *0201 || *0202 || *0303 ||
|-
| *0301 || *0202 || *0302 ||
|-
| *0302 || || ||
|-
| *0303 || *0301 || *0602 ||
|-
| *0401 || *0303 || *0401 || *0402
|-
| *0501 || *0201 || ||
|-
| *0505 || *0301 || ||
|-
| *0601 || *0301 || ||
|-
| colspan = 8 | See haplotype table in HLA-DQ
. Unbolded are rare haplotypes
|-
| colspan = 8 | Link to haplotypes can be followed by DQB1 alleles
|}
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...
present on short arm of chromosome 6 (6p21.3) 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...
which 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-DQA1 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 ....
alpha 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 alpha chain 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, exon
Exon
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 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 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.
DQ1
There are four commonly encountered DQA1 alleles: DQA1*0101, *0102, *0103, *0104. These alleles are always found in haplotypes with HLA-DQB1*05 (DQ5HLA-DQ5
HLA-DQ4 is a human leukocyte antigen serotype subgroup within HLA-DQ serotypes. The serotype is determined by the antibody recognition of β5.x subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ5 are encoded by the HLA-DQB1*05 allele group. This group currently contains 4...
) and HLA-DQB1*06 (DQ6
HLA-DQ6
HLA-DQ6 is a human leukocyte antigen serotype within HLA-DQ serotype group. The serotype is determined by the antibody recognition of β6 subset of DQ β-chains. The β-chain of DQ isoforms are encoded by HLA-DQB1 locus and DQ6 are encoded by the HLA-DQB1*06 allele group. This group currently...
). DQ1 is a serotype, rare among serotypes for human class II antigens, in that the antibodies to DQ1 react to the alpha chain of HLA DQ, these DQA1 allele gene products.
| DQA1 | linked DQB1 allele | ||||||
| DQ1 HLA-DQ1 HLA-DQ1 is a serotype that covers a broad range of HLA-DQ haplotypes. Historically it was identified as a DR-like alpha chain called DC1, later, it was among 3 types DQw1 , DQw2 and DQw3. Of these three serotyping specificities only DQw1 recognized DQ alpha chain. The serotype is positive in... |
*0101 | *0501 | *0301 | ||||
| *0102 | *0502 | *0504 | *0602 | *0604 | *0605 | *0609 | |
| *0103 | *0501 | *0502 | *0601 | *0602 | *0603 | ||
| *0104 | *0501 | *0503 | *0602 | ||||
| *0105 | rare | ||||||
| *0106 | rare | ||||||
| See haplotype table in HLA-DQ 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... . Unbolded are rare haplotypes |
|||||||
| Link to haplotypes can be followed by DQB1 alleles | |||||||
Other
The other DQA1 alleles have no defined serotype. There are 5 groups, DQA1*02, *03, *04, *05, *06. DQA1 within these groups are either invariant or produce the same α-chain subunit. DQA1*02 and DQA1*06 contain only one allele. DQA1*03 has three alleles which each produce nearly identical α3. For DQA1*05, the DQA1*0501 and DQA1*0505 produce identical α5. Other DQA1*05 exist that produce variant α5var, but these are rare.{| class = "wikitable"
|+ HLA-DQA1 alleles
! DQA1 || colspan = 6 | linked DQB1 allele
|-
| *0201 || *0202 || *0303 ||
|-
| *0301 || *0202 || *0302 ||
|-
| *0302 || || ||
|-
| *0303 || *0301 || *0602 ||
|-
| *0401 || *0303 || *0401 || *0402
|-
| *0501 || *0201 || ||
|-
| *0505 || *0301 || ||
|-
| *0601 || *0301 || ||
|-
| colspan = 8 | See haplotype table in HLA-DQ
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...
. Unbolded are rare haplotypes
|-
| colspan = 8 | Link to haplotypes can be followed by DQB1 alleles
|}