elk , Tissue-Specific ets -Related Genes on Chromosomes X and 14 Near Translocation Breakpoints

Abstract

The myb-ets-containing acute leukemia virus, E26, transforms myeloblasts and erythroblasts in culture and causes a mixed erythroid and myeloid leukemia in chicks. Genes (ets-1, ets-2, and erg) with variable relatedness to the v-ets oncogene of the E26 virus have been identified, cloned, and characterized in several species. Two new members (elk-1 and elk-2) of the ets oncogene superfamily have now been identified. Nucleotide sequence analysis of the elk-1 cDNA clone revealed that this gene encodes a 428-residue protein whose predicted amino acid sequence showed 82% similarity to the 3' region of v-ets. The elk or related sequences appear to be transcriptionally active in testis and lung. The elk cDNA probe detects two loci in the human genome, elk-1 and elk-2, which map to chromosome regions Xp11.2 and 14q32.3, respectively. These loci are near the translocation breakpoint seen in the t(X;18) (p11.2;q11.2), which is characteristic of synovial sarcoma, and the chromosome 14q32 breakpoints seen in ataxia telangiectasia and other T cell malignancies. This suggests the possibility that rearrangements of elk loci may be involved in pathogenesis of certain tumors.

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

“…A small di erence observed between the deduced and actual molecular weight of the Fli-1 proteins may be because of the presence of high proline content. A similar phenomenon was observed with Erg-2 and Elk-1 proteins (Rao et al, , 1989. The expression of splice variant Fli-1b mRNA was examined by Northern blot analysis of Poly(A) + RNAs isolated from Molt-4 (human T-cell acute lymphoblastic leukemia), Colo 320 (human colon adenocarcinoma), KG-1 (human acute myelogenous leukemia) and 697 (human pre-B cell acute lymphocytic leukemia) cells.…”

“…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.…”

Induction of apoptosis by Elk-1 and ΔElk-1 proteins

“…Elk-1, SAP1, and NET/ ERP/SAP2/Elk-3 (Rao et al, 1989;Hipskind et al, 1991;Giovane et al, 1994;Lopez et al, 1994;Dalton and Treisman, 1992;Price et al, 1995;Nozaki et al, 1996). The Elk-1 gene codes for at least two alternately spliced products Elk-1 (Rao et al, 1989) and DElk-1 (Rao and Reddy, 1993) which function as transcriptional activators (Rao and Reddy, 1992;Bhattacharya et al, 1993), are substrates for MAP kinases Marias et al, 1993;Hill et al, 1993) and JNK protein kinases (Gupta et al, 1996;Whitmarsh et al, 1995). As mentioned earlier, the Elk-1 protein is a TCF which in association with serum response factor (SRF) forms a ternary complex on the serum response element (SRE) of the c-fos promoter and regulates cfos transcription (Hipskind et al, 1991).…”

“…The TCF's which includes Elk-1 have three domains with similar sequences and functions. The ets domain mediates DNA binding, the SRF interaction domain interacts with SRF to form a ternary complex with the c-fos SRE and the C-terminal domain activates transcription upon phosphorylation by MAP kinases (Rao et al, 1989;Rao and Reddy, 1992;Dalton and Treisman, 1992;Janknecht et al, 1993Janknecht et al, , 1994Marias et al, 1993;Giovane et al, 1994;Hipskind et al, 1994;Kortenjann et al, 1994;Lopez et al, 1994;Hill et al, 1995;Price et al, 1995;Whitmarsh et al, 1995) and JNK kinases (Gupta et al, 1996). Thus Elk-1 represents a key link between signal transduction and induction of gene transcription.…”

“…The Elk-1 and DElk-1 transfected cells showed accelerated rates of apoptosis (Ap value 49% for Rat-1 Elk-1, 66% for MCF-7 Elk-1, 42% for Rat-1 DElk-1 and 28% for MCF-7 DElk-1 cells) in the presence of calcium ionophore (Figure 3a and b) Figure 1 Detection of Elk-1 and DElk-1 proteins in Rat-1, Rat-1 Elk-1 and Rat-1 DElk-1 cells by immunohistochemistry. Full length Elk-1 (Rao et al, 1989) and DElk-1 cDNA's were subcloned into pcDNA expression vectors. Puri®ed DNA (20 mg) of pcDNA expression vector or vector containing Elk-1/DElk-1 cDNA's were transfected into Rat-1 and MCF-1 cells by calcium phosphate precipitation method using the Invitrogen kit as described previously .…”