Interleukin-3 dependent c-myc protein expression during the cell cycle of murine mast cells.
Aim of the study was to evaluate the relationship between the mitogenic stimulus interleukin-3 to normal murine mast cells and the cell cycle dependent expression of the nuclear c-myc protein. In order to do that on a cell by cell basis, we measured the nuclear c-myc protein simultaneously by flow cytometry, via specific monoclonal antibodies, and the DNA content via the intercalating dye propidium iodide. When cells were deprived from interleukin-3 (IL-3), proliferation was inhibited and the majority of cells arrested in early G1 (G1A, characterized by low c-myc content). Readdition of IL-3 resulted in a slow transition of cells from G1A to late G1 (G1B, at higher c-myc content) before DNA synthesis started. G1A cells with low c-myc content do not undertake DNA synthesis. Using a stathmokinetic methodology we confirmed that the G1A cells are early postmitotic G1 phase cells. The low content of c-myc within these cells appears a direct consequence of reduced c-myc levels during mitosis. Cumulatively, the data suggest that c-myc protein levels of murine mast cells fall at mitosis and that these levels must rise before cells can traverse the G1 phase. Our data are compatible with a model in which c-myc protein content of G1 phase cells has to reach a critical threshold before the cells can move further into the cell cycle.
Minks
M
M
Laboratorio di Biofisica, Istituto Nazionale per la Ricerca sul Cancro (IST), Genova, Italy.
Di Vinci
A
A
Bruno
S
S
Geido
E
E
Avignolo
C
C
Giaretti
W
W
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry; D016193:G1 Phase; D015870:Gene Expression / Q000187:drug effects; D007377:Interleukin-3 / Q000494:pharmacology*; D008407:Mast Cells / Q000166:cytology / Q000187:drug effects*; D051379:Mice; D016271:Proto-Oncogene Proteins c-myc / Q000032:analysis*
D007377:Interleukin-3; D016271:Proto-Oncogene Proteins c-myc; D004247:DNA