INTERLEUKIN-3 DEPENDENT C-MYC PROTEIN EXPRESSION DURING THE CELL-CYCLE OF MURINE MAST-CELLS

MINKS M DIVINCI A BRUNO S GEIDO E AVIGNOLO C GIARETTI W

M. Minks et al., INTERLEUKIN-3 DEPENDENT C-MYC PROTEIN EXPRESSION DURING THE CELL-CYCLE OF MURINE MAST-CELLS, Cancer letters, 62(3), 1992, pp. 243-249

29

INGLESE

Article

Cancer letters → ACNP

0304-3835

62

3

1992

243 - 249

ISI

0304-3835(1992)62:3<243:IDCPED>2.0.ZU;2-T

Aim of the study was to evaluate the relationship between the mitogeni c stimulus interleukin-3 to normal murine mast cells and the cell cycl e dependent expression of the nuclear c-myc protein. In order to do th at on a cell by cell basis, we measured the nuclear c-myc protein simu ltaneously 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 o f 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 D NA 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 l evels during mitosis. Cumulatively, the data suggest that c-myc protei n levels of murine mast cells fall at mitosis and that these levels mu st rise before cells can traverse the G1 phase. Our data are compatibl e 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.