The c-ets-1 protein is chromatin associated and binds to DNA in vitro

The c-ets-1 proto-oncogene is expressed at high levels in proliferating lymphoid cells. We show here that the chicken and murine c-ets-1 proteins are predominantly localized in the cell nucleus. Over 90% of the c-ets-1 protein can be released from isolated thymocyte nuclei by treatment with low salt buffer. Release from nuclei is also observed after treatment with micrococcal nuclease, but not with RNaseA, in conditions where digestion of only a minor fraction of chromatin occurs. c-ets-1 proteins exhibit DNA binding activity, suggesting that the association to chromatin is mediated at least in part by their association to DNA. We previously showed that mitogenic stimulation of thymocytes is accompanied by the rapid calcium-dependent phosphorylation of c-ets-1 proteins. We demonstrate here that these phosphorylation events abolish the ability of c-ets-1 proteins to bind to DNA in vitro and reduce their affinity for chromatin, lending further support to the importance of these modifications in the regulation of c-ets-1 protein function.