Influence of nucleotides flanking the ggaa core sequence on ets1 and ets2 DNA-binding activity and the mechanism of ets1 autoregulation.

The Ets family of genes encode nuclear proteins that activate transcription by binding to a specific purine-rich (GGAA) ets binding sequence (EBS) present in promoters/enhancers of various genes. We have previously shown that over-expression of ets1 via transfection of ets1 expression vectors into NIH3T3 cells induced the expression of the endogenous Ets1 gene. Here we report that the autoregulation occurs as a result of the ets1 protein binding to the EBS-core located in its own promoter. In the present study, we have also identified Ets binding sites in the IL-4, G-CSF (granulocyte colony stimulating factor), and the 2'5' OAS (oligoadenylate synthetase) promoters by binding with Ets1 and Ets2 proteins using electrophoretic mobility shift assays. Interestingly, we have found that the EBS containing T nucleotides on either side of the GGAA core sequence, does not bind Ets1 or Ets2 proteins. Our findings demonstrate that the sequences surrounding the purine core - GGAA- have a profound influence on the binding of Ets proteins.