<p>[PROBLEMS] To find a protein capable of interacting with RUNX to regulate the action of RUNX, provide a means for regulating the action of RUNX and provide a means useful for the prevention and/or treatment of a disease caused by RUNX abnormality. [MEANS FOR SOLVING PROBLEMS] It is found that NEDD4 which is a HECT E3 ligase can ubiquitinate RUNX to cause the degradation of RUNX. Based on this finding, there are provided a method for the ubiquitination of RUNX or a method for the degradation of RUNX which is characterized by using NEDD4; a ubiquitinating agent or a degrading agent for RUNX; a method for the inhibition of the ubiquitination or the degradation of RUNX by NEDD4; a ubiquitination inhibitor or a degradation inhibitor for RUNX; a method for the identification of a compound capable of inhibiting or enhancing the ubiquitination of RUNX; a method for the identification of a compound capable of inhibiting or enhancing the binding between RUNX and NEDD4; a reagent kit; and a method for the prevention and/or treatment of a disease caused by RUNX abnormality.</p>
