Transcription factor PU.1 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''SPI1''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
This gene encodes an ETS-domain transcription factor that activates gene expression during myeloid and B-lymphoid cell development. The nuclear protein binds to a purine-rich sequence known as the PU-box found on enhancers of target genes, and regulates their expression in coordination with other transcription factors and cofactors. The protein can also regulate alternative splicing of target genes. Multiple transcript variants encoding different isoforms have been found for this gene.
The PU.1 transcription factor is essential for
hematopoiesis
Haematopoiesis (; ; also hematopoiesis in American English, sometimes h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten ...
and
cell fate Within the field of developmental biology, one goal is to understand how a particular cell develops into a specific cell type, known as fate determination. In an embryo, several processes play out at a molecular level to create an organism. These pr ...
decisions. PU.1 can physically interact with a variety of regulatory factors like
SWI/SNF
In molecular biology, SWI/SNF (SWItch/Sucrose Non-Fermentable), is a subfamily of ATP-dependent chromatin remodeling complexes, which is found in eukaryotes. In other words, it is a group of proteins that associate to remodel the way DNA is packa ...
,
TFIID
Transcription factor II D (TFIID) is one of several general transcription factors that make up the RNA polymerase II preinitiation complex. RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters ...
,
GATA-2,
GATA-1
GATA-binding factor 1 or GATA-1 (also termed Erythroid transcription factor) is the founding member of the GATA family of transcription factors. This protein is widely expressed throughout vertebrate species. In humans and mice, it is encoded b ...
and
c-Jun
Transcription factor Jun is a protein that in humans is encoded by the ''JUN'' gene. c-Jun, in combination with protein c-Fos, forms the AP-1 early response transcription factor. It was first identified as the Fos-binding protein p39 and only l ...
. The protein-protein interactions between these factors can regulate PU.1-dependent cell fate decisions. PU.1 can modulate the expression of 3000 genes in hematopoietic cells including
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 ...
. It is expressed in
monocytes
Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and monocyte-derived dendritic cells. As a part of the vertebrate innate immune system monocytes also i ...
,
granulocytes
Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that ...
,
B and
NK cells
Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. They are a kind of large granular lymphocytes (LGL), and belong to the rapidly expanding family of known innate lymphoid cell ...
but is absent in
T cells
T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their ce ...
,
reticulocytes
In hematology, reticulocytes are immature red blood cells (RBCs). In the process of erythropoiesis (red blood cell formation), reticulocytes develop and mature in the bone marrow and then circulate for about a day in the blood stream before ...
and
megakaryocytes
A megakaryocyte () is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but ca ...
. Its transcription is regulated by various mechanisms .
PU.1 is an essential regulator of the pro-fibrotic system. In
fibrotic conditions, PU.1 expression is perturbed in fibrotic diseases, resulting in upregulation of fibrosis-associated genes sets in
fibroblasts
A fibroblast is a type of biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibrobla ...
. Disruption of PU.1 in fibrotic fibroblasts leads to them returning into their resting state from pro-fibrotic fibroblasts. PU.1 is seen to be highly expressed in
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and bio ...
producing-fibrotic fibroblasts while it is downregulated in
inflammatory/ ECM degrading and resting fibroblasts. The majority of the cells expressing PU.1 in fibrotic conditions remain to be fibroblasts with a few infiltrating
lymphocytes
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells (for cell-mediated and cytotoxic adaptive immunity), B cells (for humoral, antibody-driven adaptive immunity), and ...
. PU.1 induces the polarization of resting and inflammatory fibroblasts into fibrotic fibroblasts.
Structure
The ETS domain is the DNA-binding module of PU.1 and other ETS-family transcription factors.
Interactions
SPI1 has been shown to
interact
Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization advocating for the legal and human rights of children with intersex traits. The organization was founded in 2006 and fo ...
with:
*
FUS,
*
GATA2
GATA2 or GATA-binding factor 2 is a transcription factor, i.e. a nuclear protein which regulates the expression of genes. It regulates many genes that are critical for the embryonic development, self-renewal, maintenance, and functionality of ...
,
*
IRF4
Interferon regulatory factor 4 (IRF4) also known as MUM1 is a protein that in humans is encoded by the ''IRF4'' gene. IRF4 functions as a key regulatory transcription factor in the development of human immune cells.Nam S, Lim J-S (2016). "Essentia ...
,
and
*
NONO
Nono may refer to:
Places
* Nono, Argentina, a municipality in the Province of Córdoba
* Nono, Ecuador, a parish in the municipality of Quito in the province of Pichincha
* Nono, Illubabor, Oromia (woreda), Ethiopia, or Nono Sele
** Nono, Illub ...
.
References
Further reading
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
External links
*
{{Transcription factors
Transcription factors