Dual specificity tyrosine-phosphorylation-regulated kinase 1A is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the DYRK1A gene

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...

. Alternative splicing of this gene generates several transcript variants differing from each other either in the 5' UTR or in the 3' coding region. These variants encode at least five different isoforms.

Function

DYRK1A is a member of the dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family. This member contains a nuclear targeting signal sequence, a protein kinase

Protein kinase

A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them . Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins...

 domain, a leucine zipper

Leucine zipper

A leucine zipper, aka leucine scissors, is a common three-dimensional structural motif in proteins. These motifs are usually found as part of a DNA-binding domain in various transcription factors, and are therefore involved in regulating gene expression...

 motif, and a highly conservative 13-consecutive-histidine repeat. It catalyzes its autophosphorylation

Autophosphorylation

In biochemistry, autophosphorylation is the process in which a protein kinase attaches a phosphate group to itself. This usually lead to kinase activation or regulation, and phosphorylation of other kinase substrates....

 on serine/threonine and tyrosine residues. It may play a significant role in a signaling pathway regulating cell proliferation and may be involved in brain development. This gene is a homolog of Drosophila mnb (minibrain) gene and rat Dyrk gene.

Dyrk1a has also been shown to modulate plasma homocysteine

Homocysteine

Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...

 level in a mouse model of overexpression.

Clinical significance

DYRK1A is localized in the Down syndrome

Down syndrome

Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

critical region of chromosome 21, and is considered to be a strong candidate gene for learning defects associated with Down syndrome. In addition, a polymorphism (SNP) in DYRK1A was found to be associated with HIV-1 replication in monocyte-derived macrophages, as well as with progression to AIDS in two independent cohorts of HIV-1-infected individuals.