Expression of the cyclic AMP-dependent transcription factors, CREB, CREM and ATF2, in the human myometrium during pregnancy and labour.

Elevated concentrations of cyclic AMP (cAMP) in the human myometrium may promote uterine quiescence during pregnancy by protein kinase A (PKA)-mediated phosphorylation and subsequent inactivation of myosin light-chain kinase, as well as by the phosphorylation and activation of cAMP-dependent transcription factors. In this context, we show that the altered expression of cAMP response-element binding protein (CREB), cAMP response-element modulator protein (CREM) and activating transcription factor 2 (ATF2) are implicated in the maintenance of myometrial quiescence during fetal maturation and the switch to uterine activation at term. Using electrophoretic mobility shift and super shift assays, as well as immunoblotting of paired myometrial tissue samples from non-pregnant, pregnant non-labouring and spontaneous labouring women, we defined the patterns of expression of various isoforms of these proteins in the human uterus. Here, we report spatio-temporal changes in the expression of a 43 kDa form of CREB, a 28 kDa CREM-like protein, and a novel 28 kDa ATF2-like protein which are differentially expressed, depending on the gestational state of the uterus. Changes in the pattern of expression of these potent transcription factors may have an important role in the control of uterine activity throughout pregnancy.