Hematopoietically-expressed homeobox protein HHEX is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans is encoded by the ''HHEX''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
and also known as Proline Rich Homeodomain protein PRH.
This gene encodes a member of the
homeobox
A homeobox is a DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. For instance, mutations in a homeobox may change large-scale anatomical features of the full-g ...
family of
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...
s, many of which are involved in developmental processes. Expression in specific hematopoietic lineages suggests that this protein may play a role in
hematopoietic
Haematopoiesis (, from Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cell ...
differentiation but the expression of this protein is not limited to hematopoietic cells.
Function
The HHEX transcription factor acts as a activator of transcription in some instances and a repressor of transcription others.
It interacts with a number of other signaling molecules to play an important role in the development of multiple organs, such as the liver, thyroid and forebrain.
HHEX serves to repress VEGFA, another protein which is important in endothelial cell development.
SCL, a significant transcription factor for blood and endothelial cell differentiation, is shown to interact with HHEX to promote the correct development of the hematopoiesis process.
HHEX appears to work together with another molecule, β-catenin, for the development of the anterior organizer.
It also contributes to developmental remodeling and stabilization of endothelial cells in an unborn organism.
The importance of this transcription factor is illustrated by the inability of HHEX knockout mice embryos to survive gestation. Without the expression of HHEX, these mice embryos die in utero between Day 13 and Day 16.
HHEX knockout mice display a range of abnormalities including forebrain abnormalities in various levels of severity, as well as a number of other defects including heart, vasculature, liver, monocyte, and thyroid abnormalities.
The HHEX protein is important in a variety of cancers and it can act as an tumour suppressor protein or as an oncoprotein depending on the cancer type.
Interactions
HHEX has been shown to
interact
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with
Promyelocytic leukemia protein.
References
Further reading
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External links
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{{Transcription factors, g3
Transcription factors