ETS Family Proteins Activate Transcription from HIV-1 Long Terminal Repeat

Abstract

ets is a multigene family and its members share a common ETS DNA-binding domain. ETS proteins activate transcription via binding to a purine-rich GGAA core sequence located in promoters/enhancers of various genes, including several that are transcriptionally active in T cells. The ETS1, ETS2, and ERBG/Hu-FLI-1 gene expression pattern also suggests a role for these genes in cells of hematopoietic lineage. The HIV-1 LTR core enhancer contains two 10-base pair direct repeat sequences (left and right) that are required for regulation of HIV-1 mRNA expression by host transcription factors, including NF kappa B. Two ETS-binding sites are present in the core enhancer of all the HIV-1 isolates reported so far. In our studies, we utilized HIV-1 HXB2 and HIV-1 Z2Z6 core enhancers because the Z2Z6 strain has a single point mutation flanking the right ETS-binding site. We demonstrate that the ETS1, ETS2, and ERGB/Hu-FLI-1 proteins can trans-activate transcription from both the HXB2 and Z2Z6 core enhancer when linked to a reporter (cat) gene. In addition, we show that the DNA binding and trans-activation with the Z2Z6 core enhancer is at least 40-fold higher than that observed with the HXB2 core enhancer. Further, we provide evidence that the marked increase in binding and trans-activation with Z2Z6 core enhancer sequences is due to the substitution of a flanking T residue in HXB2 TGGAA) by a C residue in Z2Z6 (CGGAA) isolate, thus generating an optimal ETS-binding core (CGGAA) sequence.

Transcription Factors Ets1, NF-κB, and Sp1 Are Major Determinants of the Promoter Activity of the Human Protein Kinase CK2α Gene

“…The pairwise presence of Ets1 motifs seen with the CK2␣ gene promoter seems to be a rather common feature. It has also been reported for genes such as the human T-cell receptor ␣ gene (38) or all known HIV1 genes (39), and it seems to relate to a low Ets1 binding affinity of individual Ets1 sites and to DNaseI footprints, which are significantly larger than a minimal Ets-1 binding site (38). Interestingly, in a number of promoters that lack a TATA box, Ets motifs are located close to the transcription initiation sites (40) proposed that Ets-family binding sites in TATA-less promoters may function similarly to Sp1 in TFIID recruitment and preinitiation complex formation by the general mechanisms, resulting in transcriptional activity (49).…”

Upregulation of Id2, an oncogenic helix-loop-helix protein, is mediated by the chimeric EWS/ets protein in Ewing sarcoma

“…The luminescence intensity is expressed as a ratio of reporter vector to the phRL-TK reference vector, and the wild type (IdL-wild or IdS-wild) is regarded as 1.0 Experiments were repeated twice and each experiment was performed on duplicate wells (Wasylyk et al, 1990;Pankov et al, 1994), Sp-1 (Seth et al, 1993), and c-myb (Dudek et al, 1992) has been reported. In addition, DNA-binding motifs, that is, AP2, CEBP, GRE, E-box, CREB, AP-1, and SP-1, correlate with enhanced ets activity (Edelman et al, 2000).…”

Regulation of Ets function by protein–protein interactions

“…Adjacent or overlapping binding sites for Ets and NFkB are present in many inducible lymphoid genes, including IL-2, IL2-receptor (John et al, 1995), IL-3 (Gottschalk et al, 1993), GM-CSF (Thomas et al, 1997), IL-12 (Gri et al, 1998), viral genes including the HIV-I enhancer (Seth et al, 1993) and signaling molecules, such as protein kinase CK2a (Krehan et al, 2000). Co-transfection of NFkB and Ets contributes to synergistic transcription activation of HIV-I and HIV-II , GM-CSF (Thomas et al, 1997), IL-2Ra (John et al, 1995) and IL-12 (Gri et al, 1998).…”