CHANGES IN DISTRIBUTION OF ACTIN MESSENGER-RNA IN DIFFERENT POLYSOME FRACTIONS FOLLOWING STIMULATION OF MPC-11 CELLS

Individual mRNA species have been shown to differ both with respect to localization in the cell, and in their distribution upon stimulation of cells with different signals. In this study we have examined the di stribution of actin mRNA in the free, cytoskeletal-bound, and membrane -bound RNA fractions, both in starved cells, and in response to stimul ation by feeding. These results were then compared with mRNAs for glyc eraldehyde 3-phosphate dehydrogenase (GAPDH), and histone H4. The resu lts we obtained showed that actin mRNA was located in the free RNA fra ction in starved cells, while upon stimulation it was located both in the free, and in the cytoskeletal fraction; no redistribution of GAPDH mRNA occurred between the three RNA fractions, while H4 mRNA showed a different localization upon stimulation. Incubation with the drugs ac tinomycin-D and cycloheximide showed that an altered localization of a ctin mRNA from free in starved cells to free and cytoskeletal mRNA fra ctions following stimulation, was dependent on RNA synthesis, and not on protein synthesis.