Dw. Mcferran et al., Persistent synchronized oscillations in prolactin gene promoter activity in living pituitary cells, ENDOCRINOL, 142(7), 2001, pp. 3255-3260
PRL gene expression in the anterior pituitary gland responds rapidly to dif
ferent hormonal signals. We have investigated the long-term timing of trans
criptional activation from the PRL, GH, and cytomegalovirus promoters in re
sponse to different stimulus duration, using real-time imaging of luciferas
e expression in living stably transfected GH3 cells. Long-term stimulation
of serum-starved cells with 50% serum induced a homogeneous rise in PRL pro
moter activity, with subsequent heterogeneous fluctuations in luciferase ac
tivity in individual cells. When cells were subjected to a 2-h pulse of 50%
serum, followed by serum-fi ee medium, there were long-term (approximately
50 h) synchronized, homogeneous oscillations in PRL promoter activity. Thi
s response was PRL-specific, because in GH3 cells expressing luciferase fro
m the GH or cytomegalovirus promoters, a serum pulse elicited no oscillatio
ns in luciferase expression after an initial transient response to serum. T
he PRL promoter may therefore be a template for an unstable transcription c
omplex subject to stochastic regulation, allowing an oscillatory transcript
ional response to physiological signals. This suggests that precise timing
and coordination of cell responses to different signal-duration may represe
nt a novel mechanism for coordinating long-term dynamic changes in transcri
ption in cell populations.