The human EVI1 gene spans approximately 65 kb of genomic DNA. 14 of its 16 exons are coding (Fig. 1A). Transcription can initiate from alternative exons 1a, 1b, 1c, 1d, or 3L (Fig. 1B), and several alternative splice variants of the EVI1 mRNA have been described (Delta324, -Rp9, Delta105; Fig. 1A).
The human MDS1 gene consists of 4 exons spread over a genomic region of more than 500 kb. MDS1 exon 4 is located less than 2 kb upstream of EVI1 exon1a. MDS1 can also be expressed on its own. The MDS1/EVI1 mRNA presumably results from splicing of the second exon of MDS1 to the second exon of EVI1 (Fig. 1B).

Telomere to centromere.

Exon 3 of the human EVI1 gene contains two closely spaced ATG codons, either of which may serve as the translation initiation site. Depending on which ATG is used, proteins of 1051 or 1041 amino acids will be formed. EVI1 contains two domains of seven and three zinc finger motifs, respectively, a repression domain between the two sets of zinc fingers, and an acidic domain at its C-terminus. It is a 145 kDa protein that is capable of binding to DNA in a sequence specific manner, and that interacts with transcriptional coactivators and corepressors as well as other sequence specific transcription factors. DNA binding and transcriptional regulation by EVI1 are influenced by posttranslational modifications like phosphorylation, acetylation, and sumoylation (Chakraborty et al, 2001; Shimahara et al, 2010; Bard-Chapeau et al, 2013; Singh et al, 2013; White et al, 2013).
Predicted translation of MDS1-EVI1 adds 188 amino acids to the N-terminus of EVI1. 63 of these additional amino acids are encoded by exon 2 and beginning of exon 3 of EVI1, and the remaining 125 from the MDS1 gene. MDS1-EVI1 contains a PR domain, which is about 40% homologous to the N-terminus of the retinoblastoma-binding protein, RIZ, and the PRDI-BF1 transcription factor. Some biological functions of MDS1/EVI1 were reported to be different from, or even antagonistic to, those of EVI1, while in other cases, EVI1 and MDS1/EVI1 acted in a similar manner. MDS1/EVI1 (PRDM3) has H3K9me1 methyltransferase activity and a role in maintaining heterochromatin integrity (Pinheiro et al, 2012).

Among human tissues/organs, the EVI1 mRNA is expressed abundantly in kidney, lung, pancreas, stomach, ovaries, uterus, and prostate, to a lesser extent in the small intestine, colon, thymus, spleen, heart, brain, testis, and placenta, and at very low levels in skeletal muscle and bone marrow. The pattern of expression of MDS1-EVI1 is very similar to that of EVI1.
In the adult mouse, the Evi1 mRNA is expressed, at varying levels, in the kidney, lung, stomach, ovary, uterus, intestine, thymus, spleen, heart, brain, and liver. In the mouse embryo, Evi1 mRNA levels are high in the urinary system and Mullerian ducts, the lung, the heart, and the emerging limb buds.
Similar Evi1 expression patterns were also observed in Xenopus, chicken, and zebrafish.
In human and murine hematopoiesis, EVI1 mRNA levels are high in the most immature cell populations and decline in the course of differentiation (Kataoka et al, 2011; Bindels et al, 2012; Steinleitner et al, 2012).
EVI1 expression is regulated by RUNX1 and ELK1, by retinoic acid via RAR/RXR, and by certain MLL fusion proteins (Bingemann et al, 2009; Arai et al, 2011; Maicas et al, 2013).

Nuclear; in part in speckles.

Because of the spatially and temporally restricted expression of MECOM, it has been suggested that this gene plays important roles in development and could be involved in organogenesis, cell migration, cell growth, and differentiation.
In the mouse, homozygous disruption of the 6th exon of the Evi1 gene led to embryonic lethality, with widespread hypocellularity, reduced body size, small or absent limb buds, a pale yolk sac and placenta, abnormal development of the nervous system and the heart, and massive haemorrhaging. (Hoyt et al, 1997). Functions of Evi1 and/or Mds1/Evi1 in heart development, spine formation, and, particularly, maintenance and expansion of hematopoietic stem cells (HSCs) have been deduced from, or confirmed through, the phenotypes of additional MECOM knockout models (Goyama et al, 2008; Kataoka et al, 2011; Zhang et al, 2011; Bard-Chapeau et al, 2014; Juneja et al, 2014). A role of Evi1 in HSCs was also corroborated through overexpression and gene marking experiments (Buonamici et al, 2004; Laricchia-Robbio et al, 2008; Dickstein et al, 2010; Kataoka et al, 2011).
Support for a role of Evi1 as a leukemia initiating and promoting oncogene has been obtained through mouse bone marrow transduction/transplantation models, in which overexpression of Evi1 alone caused a myelodysplastic syndrome (MDS) like disease, while its co-expression with other oncogenes led to AML (Buonamici et al, 2004; Jin et al, 2007; Watanabe-Okochi et al, 2008; Watanabe-Okochi et al, 2013). Even more compellingly, in a human gene therapy trial for chronic granulomatous disease, activating integrations of the therapeutic vector into the MECOM locus led to clonal expansion with progression to MDS and, ultimately, AML (Stein et al, 2010). Evi1 was proposed to be essential for AML leukemia stem cell (LSC) function since its experimental down-regulation reduced leukemogenicity in several mouse models of AML (Goyama et al, 2008; Bindels et al, 2012). Evi1 expression was also associated with leukemia initiating capacity in chronic myeloid leukemia (CML) (Sato et al, 2014). A prominent role of EVI1 in therapy resistance was suggested by a number of clinical trials, and illustrated by in vitro data demonstrating that its ectopic expression reduced, and its knockdown enhanced, cellular responsiveness to chemotherapeutic drugs (Bindels et al, 2012; Konantz et al, 2012; Yamakawa et al, 2012; Rommer et al, 2013).
Beyond its roles in normal and malignant hematopoiesis, EVI1 negatively regulated NF-kB dependent inflammation (Xu et al, 2012) and promoted adipocyte differentiation (Ishibashi et al, 2012).
EVI1 exerts its biological functions mainly by acting as a transcription factor. and regulates the expression of both protein coding and miRNA genes. Reported direct EVI1 target genes are MS4A3 (Heller et al, 2015), PLZF (Takahashi and Licht, 2002), Gata2 (Yuasa et al; 2005), Pbx1 (Shimabe et al, 2009), Pten (Yoshimi et al, 2011), Gpr56 (Saito et al, 2013), DeltaNp63 (Nayak et al, 2013), Bcl-xL (Pradhan et al, 2011), Calreticulin (Qiu et al, 2008), Ppargamma2 (Ishibashi et al, 2012), miR-1-2 (Gomez-Benito et al, 2010), miR-9 (Senyuk et al, 2013), miR-124 (Dickstein et al, 2010), and miR-449A (De Weer et al, 2011). ChIP-seq, combined with genome wide gene expression profiling, has been employed for large-scale identification of EVI1 target genes in ovarian cancer and murine myeloid cell lines (Bard-Chapeau et al, 2012; Glass et al, 2013). EVI1 associates with a number of transcriptional cofactors like HDAC1 (Vinatzer et al, 2001), CtBP1 (Palmer et al, 2001), CtBP2 (Turner and Crossley, 1998), CBP, P/CAF (Chakraborty et al, 2001), the histone methyl transferases SUV39H1 and G9a (Spensberger et al, 2008a; Goyama et al, 2010), the ATP dependent helicases BRG1 and BRM (Chi et al, 2003), and the member of histone deacetylase complex, Mbd3b (Spensberger et al, 2008b). EVI1 was also shown to interact with DNA methyl transferases (Lugthart et al, 2011; Senyuk et al, 2011), leading to methylation of CpG islands of some of its target genes, among them, CADM1 (Fisser et al, 2014), miR-9 (Senyuk et al, 2013), and miR-124 (Dickstein et al, 2010). Furthermore, EVI1 interacted with, and modulated the function of, other sequence specific transcription factors, e.g. GATA1 (Laricchia-Robbio et al, 2006), RUNX1/AML1 (Senyuk et al, 2007), PU.1 (Laricchia-Robbio et al, 2009), SMAD3 (Kurokawa et al, 1998; Izutsu et al, 2001; Alliston et al, 2005), FOS (Bard-Chapeau et al, 2012), NFkB (Xu et al, 2012), and RAR/RXR (Bingemann et al, 2009; Steinmetz et al, 2014).
In addition to its activity as a regulator of transcription, EVI1 has been reported to inhibit c-jun N-terminal kinase (Kurokawa et al, 2000), and to stimulate PI3K/AKT signalling (Liu et al, 2006; Yoshimi et al, 2011).

EVI1 orthologs are present in many species. EVI1 proteins from other mammals share more than 90% amino acid sequence identity with the human protein, and Xenopus EVI1 is 77% identical to its human counterpart. MDS1-EVI1 shares an overall homology with the C. elegans Egl 43 protein that includes the PR domain at the N-terminus and the two zinc-finger domains. An MDS1/EVI1 ortholog, hamlet, is also present in Drosophila.