In their study, high INNO-406 molecular weight proteins were not detected. This result would be explained by the complex formation between MRTF-A and G-actin; CCG- 1423 is less likely to bind to MRTF-A associated with G-actin. The nuclear accumulation of MRTF-A occurs transiently just after serum stimulation and thereafter nuclear MRTF-A is gradually exported to the cytoplasm. Re-stimulation with fresh serum induces the nuclear accumulation of MRTF-A again. In the cytoplasm, MRTF-A forms a stable complex with G-actin. The Larsen group probably used the proliferating PC-3 cell lysates. However, for the reasons stated above, they could not detect MRTF-A/B. Our present findings provide a new strategy for anti-EMT drug discovery by focusing on the nuclear import of MRTF-A. Immobilization of small molecules on Sepharose or microplates using a photoaffinity reaction is an effective method for detection of small molecule�Cprotein interactions. This system using CCG- 1423 as the leading compound would be a useful tool for anti- EMT drug screening because non-specific binding to CCG-1423 Sepharose was not detected in our study. Furthermore, we are currently working to determine whether a high-throughput screening system could be established using a series of CCG-1423-related compounds immobilized on microarrays and purified MRTF-A protein with fluorescent tag. In conclusion, CCG-1423 binds specifically to MRTF-A under mediation by the NB, resulting in inhibition of the interaction between MRTF-A and importin a/b1. However, this inhibitory action of CCG-1423 is restricted to the conditions where the Gactin pool is depleted. A similar inhibitory action is expected be applicable to the interaction between MRTF-B or Phactr1 and importin a/b1. The CMGC group of the human GSK-573719A kinome is split into several branches, one of which, also including DYRKs and CLKs, gives rise to a sub-branch composed by so called homeodomaininteracting protein kinases
