Transfection of P311 into NIH 3T3 cells stimulates expression of SM α-actin and SM22. (a) RT-PCR showing mRNA for three SM-specific markers in cells transfected with empty vector or transfected with P311. Notice that P311 upregulated SM α-actin message, induced SM22 message and did not alter significantly the mRNA for SM-myosin, present in both control and P311-expressing cells. (b) Cells expressing P311 do not show either STM-specific markers such as STM α-actin and myoglobin or desmin, a protein present in both STM and SM. (c) Immunoblot demonstrating upregulation of SM α-actin and induction of SM22 in P311-transfected cells and absence of other SM and STM markers. The membrane used for SM22 detection was stained with Coomassie blue to show equal protein loading.