RESULTS: Using
hormone-responsive immortalized human uterine
leiomyoma (ht-UtLM) cells, we found that
genistein activated MAPKp44/42 and MSK1, and also increased phosphorylation of
histone H3 at serine10 (H3S10ph) in ht-UtLM cells. Colocalization of phosphorylated MSK1 and H3S10ph was evident by confocal microscopy in ht-UtLM cells (r = 0.8533). Phosphorylation of both MSK1and H3S10ph was abrogated by
PD98059 (PD), a MEK1
kinase inhibitor, thereby supporting
genistein's activation of MSK1 and
Histone H3 was downstream of MAPKp44/42. In proliferative (estrogenic) phase human
uterine fibroid tissues, phosphorylated MSK1 and H3S10ph showed increased immunoexpression compared to normal myometrial tissues, similar to results observed in in vitro studies following low-dose
genistein administration. Real-time RT-PCR arrays showed induction of growth-related
transcription factor genes, EGR1, Elk1, ID1, and MYB (cMyb) with confirmation by western blot, downstream of MAPK in response to low-dose
genistein in ht-UtLM cells. Additionally,
genistein induced associations of promoter regions of the above
transcription factors with H3S10ph as evidenced by
Chromatin Immunoprecipitation (ChIP) assays, which were inhibited by PD. Therefore,
genistein epigenetically modified
histone H3 by phosphorylation of
serine 10, which was regulated by MSK1 and MAPK activation.
CONCLUSION: