Elf-1 contributes to the function of the complex interleukin (IL)-2-responsive enhancer in the mouse IL-2 receptor alpha gene.
Lymphocytes regulate their responsiveness to IL-2 through the transcriptional control of the IL-2R alpha gene, which encodes a component of the high affinity IL-2 receptor. In the mouse IL-2R alpha gene this control is exerted via two regulatable elements, a promoter proximal region, and an IL-2-responsive enhancer (IL-2rE) 1.3 kb upstream. In vitro and in vivo functional analysis of the IL-2rE in the rodent thymic lymphoma-derived, CD4- CD8- cell line PC60 demonstrated that three separate elements, sites I, II, and III, were necessary for IL-2 responsiveness; these three sites demonstrate functional cooperation. Site III contains a consensus binding motif for members of the Ets family of transcription factors. Here we demonstrate that Elf-1, an Ets-like protein, binds to site III and participates in IL-2 responsiveness. In vitro site III forms a complex with a protein constitutively present in nuclear extracts from PC60 cells as well as from normal CD4- CD8- thymocytes. We have identified this molecule as Elf-1 according to a number of criteria. The complex possesses an identical electrophoretic mobility to that formed by recombinant Elf-1 protein and is super-shifted by anti-Elf-1 antibodies. Biotinylated IL-2rE probes precipitate Elf-1 from PC60 extracts provided site III is intact and both recombinant and PC60-derived proteins bind with the same relative affinities to different mutants of site III. In addition, by introducing mutations into the core of the site III Ets-like motif and comparing the corresponding effects on the in vitro binding of Elf-1 and the in vivo IL-2rE activity, we provide strong evidence that Elf-1 is directly involved in IL-2 responsiveness. The nature of the functional cooperativity observed between Elf-1 and the factors binding sites I and II remains unresolved; experiments presented here however suggest that this effect may not require direct interactions between the proteins binding these three elements.
Serdobova
I
I
Lymphocyte Biology Unit, Swiss Institute for Experimental Cancer Research, Epalinges, France.
Pla
M
M
Reichenbach
P
P
Sperisen
P
P
Ghysdael
J
J
Wilson
A
A
Freeman
J
J
Nabholz
M
M
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D036383:Ephrin-A2; D007376:Interleukin-2 / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics; D050783:Proto-Oncogene Proteins c-ets; D015375:Receptors, Interleukin-2 / Q000235:genetics*; D013601:T-Lymphocytes / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C512897:ELF1 protein, human; C512896:Elf1 protein, mouse; D036383:Ephrin-A2; D007376:Interleukin-2; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D015375:Receptors, Interleukin-2; D014157:Transcription Factors