COLOCALIZATION OF ADF AND COFILIN IN INTRANUCLEAR ACTIN RODS OF CULTURED MUSCLE-CELLS

Immunofluorescence microscopy revealed that two actin-binding proteins of low molecular weight with different functional activity, ADF and c ofilin, are transported into nuclei of cultured myogenic cells to form rod structures there together with actin, when the cells were incubat ed in medium containing dimethylsulfoxide. In most cases, ADF and cofi lin colocalized in the same nuclear actin rods, but ADF appeared to pr edominate in mononucleated cells, while cofilin was present in multinu cleated myotubes. In some mononucleated cells, the nuclear actin rods were composed of ADF and actin but devoid of cofilin. An ADF homologue in mammals, destrin, was also translocated into nuclear actin rods un der similar conditions. As a nuclear transport signal sequence exists in cofilin and ADF but not in actin, ADF and/or cofilin may be respons ible for the nuclear import of actin in myogenic cells under certain c onditions.