THE ID GENE IS ACTIVATED BY SERUM BUT IS NOT REQUIRED FOR DEDIFFERENTIATION IN RAT VASCULAR SMOOTH-MUSCLE CELLS

Primary rat vascular smooth muscle cells cultured on fibronectin in the absence of serum lost smooth-muscle-specific myosin heavy chain but did not enter the cell cycle and proliferate until they were stimulated by serum. Under these conditions accumulation of Id mRNA occurred only in response to serum and was maximal during the G1 phase of the cycle.