Transcription factor PU.1 is a protein that in humans is encoded by the SPI1gene.[5]
Function
This gene encodes an ETS-domain transcription factor that activates gene expression during myeloid and B-lymphoid cell development.[6] 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.[7]
The PU.1 transcription factor is essential for hematopoiesis and cell fate decisions. PU.1 can physically interact with a variety of regulatory factors like SWI/SNF,[8]TFIID, GATA-2, GATA-1 and c-Jun. 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. It is expressed in monocytes, granulocytes, B and NK cells but is absent in T cells, reticulocytes and megakaryocytes. Its transcription is regulated by various mechanisms .[9]
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. 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 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. PU.1 induces the polarization of resting and inflammatory fibroblasts into fibrotic fibroblasts.[10]
Structure
The ETS domain is the DNA-binding module of PU.1 and other ETS-family transcription factors.
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Ray D, Culine S, Tavitain A, Moreau-Gachelin F (May 1990). "The human homologue of the putative proto-oncogene Spi-1: characterization and expression in tumors". Oncogene. 5 (5): 663–668. PMID1693183.
^Burda P, Laslo P, Stopka T (July 2010). "The role of PU.1 and GATA-1 transcription factors during normal and leukemogenic hematopoiesis". Leukemia. 24 (7): 1249–1257. doi:10.1038/leu.2010.104. PMID20520638. S2CID1941766.
Klemsz MJ, McKercher SR, Celada A, Van Beveren C, Maki RA (April 1990). "The macrophage and B cell-specific transcription factor PU.1 is related to the ets oncogene". Cell. 61 (1): 113–124. doi:10.1016/0092-8674(90)90219-5. PMID2180582. S2CID27819155.
Nguyen VC, Ray D, Gross MS, de Tand MF, Frézal J, Moreau-Gachelin F (May 1990). "Localization of the human oncogene SPI1 on chromosome 11, region p11.22". Human Genetics. 84 (6): 542–546. doi:10.1007/bf00210807. PMID2338340. S2CID22337200.
Chen H, Ray-Gallet D, Zhang P, Hetherington CJ, Gonzalez DA, Zhang DE, et al. (October 1995). "PU.1 (Spi-1) autoregulates its expression in myeloid cells". Oncogene. 11 (8): 1549–1560. PMID7478579.
Carrère S, Verger A, Flourens A, Stehelin D, Duterque-Coquillaud M (June 1998). "Erg proteins, transcription factors of the Ets family, form homo, heterodimers and ternary complexes via two distinct domains". Oncogene. 16 (25): 3261–3268. doi:10.1038/sj.onc.1201868. PMID9681824. S2CID26807714.
Sato M, Morii E, Takebayashi-Suzuki K, Yasui N, Ochi T, Kitamura Y, et al. (January 1999). "Microphthalmia-associated transcription factor interacts with PU.1 and c-Fos: determination of their subcellular localization". Biochemical and Biophysical Research Communications. 254 (2): 384–387. doi:10.1006/bbrc.1998.9918. PMID9918847.