In the context of gene regulation: transactivation is the increased rate of
gene expression
Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ...
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 (XT) is a 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, ...
of
signaling cascades 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 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
Leukemia ( also spelled leukaemia; pronounced ) is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or '' ...
primarily through this process. Its transactivator,
''Tax'''','' can interact with
p40, inducing overexpression of
interleukin 2
Interleukin-2 (IL-2) is an interleukin, which is a type of cytokine signaling molecule forming part of the immune system. It is a 15.5–16 Dalton (unit), kDa protein that regulates the activities of white blood cells (leukocytes, often ...
,
interleukin receptors,
GM-CSF and the
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
c-Fos. 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 produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...
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
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
. 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