Characterization of Spi-B, a transcription factor related to the putative oncoprotein Spi-1/PU.1.

Abstract

We have cloned a human cDNA from a new gene, spi-B, on the basis of its homology with the DNA-binding domain of the Spi-l/PU.1 putative oncogene product. spi-B codes for a protein of 262 amino acids presenting 43% overall identity with Spi-1. Its highly basic carboxy-terminal region exhibits 34% sequence identity with the DNA-binding domain of the Ets-1 protein. We showed that the Spi-B protein is able to bind the purine-rich sequence (PU box) recognized by Spi-1/PU.A and to activate transcription of a reporter plasmid containing PU boxes. Chromosome in situ hybridization allowed us to map spi-B to the 19q13.3-19q13.4 region of the human genome. spi-B, like spi-1, was found to be expressed in various murine and human hematopoietic cell lines except T lymphoid cell lines.spi-1 is a putative oncogene involved in the malignant erythroblastic transformation induced by the acutely leukemogenic Friend and Rauscher spleen focus-forming viruses (25,26). It was originally identified as a genomic locus rearranged by spleen focus-forming proviral insertion in 95% of these tumors (25,27). The transcriptional deregulation of spi-1 by insertional mutagenesis results in overexpression of the Spi-1 protein (unpublished data). The product of spi-1 is identical to the PU.1 transcriptional activator (11) that recognizes specific DNA sequences characterized by a purine-rich core sequence, 5'-GAGGAA-3' (PU box), which acts as a Spi-l/PU.1-responsive element when linked in cis to the herpes simplex virus thymidine kinase promoter (18). The DNA-binding domain of Spi-1/PU.1 is localized to the carboxy-terminal half of the protein (18), a domain which includes a region of 87 amino acids related to that of the Ets proteins. The ets gene family includes c-ets-1 and c-ets-2 (5, 48, 49), erg (37), elk-1 and elk-2 (36), E74 (7), fli-i (2), elg (33), elf-I (45), and PEA3 (51) and encodes sequence-specific DNA-binding proteins. Ets-1 and Ets-2 (4, 12, 47), 38), Erg (42), and PEA3 (51) have been shown to act as transcriptional activators. c-ets-I is the cellular progenitor of the v-ets oncogene of E26 (20,29), a retrovirus which induces predominantly an erythroleukemia in chicken and transforms both myeloid and erythroid cells in vitro (35). In addition to v-ets, the E26 genome contains the v-myb oncogene, and both oncogenes are expressed as a nuclear Gag-Myb-Ets fusion protein (3).

A novel epithelial-expressed ETS gene, ELF3: human and murine cDNA sequences, murine genomic organization, human mapping to 1q32.2 and expression in tissues and cancer

“…ETS proteins are indicated with a species pre®x; D (Drosophila), H (human), M (mouse). Proteins examined include: E74A (Burtis et al, 1990), ELF1 , NERF (Oettgen et al, 1996), PEP1 , ETS4 (Chen et al, 1992), YAN (Lai and Rubin, 1992), TEL (Golub et al, 1994), ELK1 (Rao et al, 1989), ERP , SAP1 (Dalton and Treisman, 1992), ER71 (Brown and McKnight, 1992), ERG (Rao et al, 1987), FLI1 (Ben-David et al, 1991), ETS6 (Chen et al, 1992), ETS1 (Chen, 1990), ETS2 (Watson et al, 1988), GABPa (LaMarco et al, 1991), ELG , ER81 (Monte et al, 1995), ERM (Monte et al, 1994), PEA3 (Xin et al, 1992), ETS3 (Chen et al, 1992), PU1 (Klemsz et al, 1990), and SPIB (Ray et al, 1992). Amino acids with identity to ELF3 are shaded.…”

Isolation and characterization of a chicken homologue of the Spi-1/PU.1 transcription factor

“…Transactivating properties of the chicken Spi-1/PU.1 protein In order to test the transactivation capacity of chicken Spi-1/PU.1 protein, we cotransfected HeLa cervical carcinoma cells which lack endogenous Spi-1/PU.1 proteins with the pSG5-ck-Spi-1/PU.1 expression vector and a luciferase reporter plasmid (Ray et al, 1992;Chen et al, 1995). In this reporter the luciferase expression was under the control of the thymidine kinase minimal promoter and three copies of the Spi-1/PU.1 binding site present in the c-fes promoter (ptkluc fes) (Ray-Gallet et al, 1995;Righi, unpublished results).…”

“…All members of this family share a conserved domain, the ETS domain, which is responsible for sequence speci®c DNA-binding (Karim et al, 1990). However, it is the most divergent member of the family de®ning with its most related gene Spi-B (Ray et al, 1992), the SPI subfamily (Laudet et al, 1993).…”

“…More recent analyses revealed that Spi-1/PU.1 expression is detectable in most hematopoietic lineages except T-lymphocytes (Ray et al, 1992). Studies with human CD34+ cells have shown that Spi-1/PU.1 is expressed in the earliest multipotential progenitors, upregulated during commitment to the myeloid lineage and downregulated during erythroid di erentiation (Chen et al, 1995;Voso et al, 1994).…”

Fli-1b is generated by usage of differential splicing and alternative promoter

“…Analyses of human and mouse Fli-1 cDNA sequences placed them in the ETS gene family which shows high homology within their DNA binding (ETS) domain (Ben-David et al, 1991;Prasad et al, 1992) and codes for di erent sequence-speci®c transcriptional activators. The superfamily of ETS genes includes several members: c-ets-1 (Reddy and Rao, 1988;Chen, 1988), ets-2 Boulukos et al, 1988), erg Rao et al, 1987), Elk-1 and Elk-2 (Rao et al, 1989), Pu.1/Spi-1 and Spi-1B (Goebl et al, 1990;Klemsz et al, 1990;Ray et al, 1992), E-74 (Burtis et al, 1990) Sap-1 and Sap-2 (Dalton and Triesman, 1992), GABP a (LaMarco et al, 1991), Elf-1 , PEA-3 (Xin et al, 1992), Fli-1 (Ben-David et al, 1990;Prasad et al, 1992), D-elg (Pribyl et al, 1988), ER-81 and ER-71 (Brown and McKnight, 1992), Tel (Golub et al, 1994), ERP (Lopez et al, 1994) and ETV-1 (Jeon et al, 1995). Most of the ETS proteins are related to each other by virtue of their Etsdomain, a 85-residue region capable of binding to speci®c DNA binding sequences.…”