DEMONSTRATION OF CELL-CYCLE KINETICS IN THYROID PRIMARY CULTURE BY IMMUNOSTAINING OF PROLIFERATING CELL NUCLEAR ANTIGEN - DIFFERENCES IN CYCLIC AMP-DEPENDENT AND AMP-INDEPENDENT MITOGENIC STIMULATIONS
M. Baptist et al., DEMONSTRATION OF CELL-CYCLE KINETICS IN THYROID PRIMARY CULTURE BY IMMUNOSTAINING OF PROLIFERATING CELL NUCLEAR ANTIGEN - DIFFERENCES IN CYCLIC AMP-DEPENDENT AND AMP-INDEPENDENT MITOGENIC STIMULATIONS, Journal of Cell Science, 105, 1993, pp. 69-80
In this study, experimental conditions are described that allowed us t
o follow the fate of the DNA polymerase delta-associated proliferating
cell nuclear antigen (PCNA), by immunolabeling during the overall cel
l cycle. Differences in subcellular localization or the presence of PC
NA allowed us to identify each phase of the cell cycle. Using these ce
ll cycle markers in dog thyroid epithelial cells in primary culture, w
e found unexpected differences in cell cycle kinetics, in response to
stimulations through cAMP-dependent and cAMP-independent pathways. The
se provide a new dimension to the view that the two pathways are large
ly separate, but co-operate on DNA synthesis initiation. More precisel
y, thyrotropin (TSH), acting via cAMP, exerts a potent triggering effe
ct on DNA synthesis, associated with a precocious induction of PCNA ap
pearance. This constitutes the major influence of TSH (cAMP) in determ
ining cell cycle progression, which is only partly moderated by TSH-de
pendent lengthening of S- and G2-phases.