In the context of gene regulation: transactivation is the increased rate of
gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...
triggered either by biological processes or by artificial means, through the expression of an intermediate transactivator protein.
In the context of receptor signaling, transactivation occurs when one or more receptors activate yet another;
receptor transactivation may result from the
crosstalk
In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...
of
signaling cascade
A biochemical cascade, also known as a signaling cascade or signaling pathway, is a series of chemical reactions that occur within a biological cell when initiated by a stimulus. This stimulus, known as a first messenger, acts on a receptor that ...
s or the activation of
G protein–coupled receptor hetero-oligomer subunits, among other mechanisms.
Natural transactivation
Transactivation can be triggered either by endogenous cellular or viral proteins, also called transactivators. These protein factors
act in trans (''i.e.'',
intermolecularly).
HIV
The human immunodeficiency viruses (HIV) are two species of '' Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immu ...
and
HTLV are just two of the many viruses that encode transactivators to enhance viral gene expression. These transactivators can also be linked to cancer if they start interacting with, and increasing expression of, a cellular
proto-oncogene. HTLV, for instance, has been associated with causing
leukemia primarily through this process. Its transactivator,
''Tax'''','' can interact with
p40 P40 may refer to:
Proteins
* Interleukin-12 subunit beta
* Neutrophil cytosolic factor 4
* Ribosomal protein SA
Vehicles
*
*Carro Armato P 40, an Italian tank
*Curtiss P-40 Warhawk, an American military aircraft
*Percival Prentice, a British train ...
, inducing overexpression of
interleukin 2
Interleukin-2 (IL-2) is an interleukin, a type of cytokine signaling molecule in the immune system. It is a 15.5–16 kDa protein that regulates the activities of white blood cells (leukocytes, often lymphocytes) that are responsible for ...
,
interleukin receptors,
GM-CSF and the
transcription factor c-Fos
Protein c-Fos is a proto-oncogene that is the human homolog of the retroviral oncogene v-fos. It is encoded in humans by the ''FOS'' gene. It was first discovered in rat fibroblasts as the transforming gene of the FBJ MSV (Finkel–Biskis–Jinkin ...
. HTLV infects
T-cells and via the increased expression of these stimulatory
cytokines
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
and
transcription factors, leads to uncontrolled proliferation of T-cells and hence
lymphoma.
Artificial transactivation
Artificial transactivation of a gene is achieved by inserting it into the genome at the appropriate area as transactivator gene adjoined to special promoter regions of
DNA. The transactivator gene
expresses a transcription factor that binds to specific promoter region of DNA. By binding to the
promoter region of a gene, the transcription factor causes that gene to be expressed. The expression of one transactivator gene can activate multiple genes, as long as they have the same, specific promoter region attached. Because the expression of the transactivator gene can be controlled, transactivation can be used to turn genes on and off. If this specific promoter region is also attached to a
reporter gene, we can measure when the transactivator is being expressed.
See also
*
Transrepression
*
Selective glucocorticoid receptor agonist
References
External links
* {{MeshName, Transactivators
Molecular biology