TY - JOUR
T1 - A novel isoform of microphthalmia-associated transcription factor inhibits IL-8 gene expression in human cervical stromal cells
AU - Li, Xiang Hong
AU - Kishore, A. Hari
AU - Dao, Doan
AU - Zheng, Weiming
AU - Roman, Christopher A.
AU - Word, R. Ann
PY - 2010/8
Y1 - 2010/8
N2 - Cervical ripening during pregnancy is a profound change in cervix structure and function characterized by increases in the proinflammatory cytokine IL-8 and dissolution of the cervical extracellular matrix. Relatively little is known about the molecular mechanisms that underlie these events. Here, we report identification of a novel isoform of micropthalmia-associated transcription factor in human cervical stromal cells (MiTF-CX) that is down-regulated 12-fold during cervical ripening and that represses expression of IL-8. Ectopic expression of MiTF-CX in human cervical stromal cells resulted in substantial suppression of endogenous IL-8 mRNA and protein expression, whereas expression of dominant negative MiTF-CX mutants with impaired DNA binding resulted in dramatic increases in IL-8 production. Gel shift, reporter gene, and chromatin immunoprecipitation assays revealed one strong binding site (E-box -397 CACATG-391) in the human IL-8 promoter that was crucial for mediating transcriptional repression by MiTF-CX. Moreover, we show that MiTF-CX expression in the cervix was itself positively autoregulated via two E-box motifs within a 2.1-kb promoter fragment. We therefore propose that maintenance of cervical competency during pregnancy is an active process maintained through suppression of IL-8 by the transcription factor MiTF-CX. During cervical ripening, loss of MiTF-CX would result in significant up-regulation of IL-8 mRNA and protein synthesis, thereby leading to recruitment and activation of leukocytes within the cervix and dissolution of the extracellular matrix.
AB - Cervical ripening during pregnancy is a profound change in cervix structure and function characterized by increases in the proinflammatory cytokine IL-8 and dissolution of the cervical extracellular matrix. Relatively little is known about the molecular mechanisms that underlie these events. Here, we report identification of a novel isoform of micropthalmia-associated transcription factor in human cervical stromal cells (MiTF-CX) that is down-regulated 12-fold during cervical ripening and that represses expression of IL-8. Ectopic expression of MiTF-CX in human cervical stromal cells resulted in substantial suppression of endogenous IL-8 mRNA and protein expression, whereas expression of dominant negative MiTF-CX mutants with impaired DNA binding resulted in dramatic increases in IL-8 production. Gel shift, reporter gene, and chromatin immunoprecipitation assays revealed one strong binding site (E-box -397 CACATG-391) in the human IL-8 promoter that was crucial for mediating transcriptional repression by MiTF-CX. Moreover, we show that MiTF-CX expression in the cervix was itself positively autoregulated via two E-box motifs within a 2.1-kb promoter fragment. We therefore propose that maintenance of cervical competency during pregnancy is an active process maintained through suppression of IL-8 by the transcription factor MiTF-CX. During cervical ripening, loss of MiTF-CX would result in significant up-regulation of IL-8 mRNA and protein synthesis, thereby leading to recruitment and activation of leukocytes within the cervix and dissolution of the extracellular matrix.
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U2 - 10.1210/me.2009-0320
DO - 10.1210/me.2009-0320
M3 - Article
C2 - 20573688
AN - SCOPUS:77955011229
SN - 0888-8809
VL - 24
SP - 1512
EP - 1528
JO - Molecular Endocrinology
JF - Molecular Endocrinology
IS - 8
ER -