Structure of the AML1-ETO NHR3 domain - type II cAMP-dependent protein kinase regulatory subunit complex and its contribution to AML1-ETO activity

AML1-ETO is the chimeric protein product of the t(8;21) in acute myeloid leukemia. The ETO portion of the fusion protein includes the Nervy Homology Region 3 (NHR3) domain, which shares some homology with A-Kinase Anchoring Proteins (AKAPs) and interacts with the regulatory subunit of type II cAMP-dependent Protein Kinase (PKA(RIIalpha)). It is possible that AML1-ETO's ability to interact with PKA(RIIalpha) might be important for t(8;21) leukemogenesis. We determined the solution structure of a complex between the AML1-ETO NHR3 domain and PKA(RIIalpha). Based on the structure, a key residue in AML1-ETO for PKA(RIIalpha) association was mutated. This mutation did not disrupt AML1-ETO's ability to enhance the clonogenic capacity of primary mouse bone marrow cells, and do not eliminate its ability to repress proliferation or granulocyte differentiation. In addition, a mouse model showed that disruption of PKA(RIIalpha) recruitment had no affect on the ability of AML1-ETO to induce leukemia in mice. Therefore, the NHR3 domain/PKA(RIIalpha) protein interaction appears to contribute relatively little to AML1-ETO's overall activity.