Dynamic expression and activity of NF-kappa B during post-natal mammary gland morphogenesis

The RelNF-kappaB family of transcription factors has been implicated in suc h diverse cellular processes as proliferation, differentiation, and apoptos is, As each of these processes occurs during post-natal mammary gland morph ogenesis, the expression and activity of NF-kappaB factors in the murine ma mmary gland were examined. Immunohistochemical and immunoblot analyses reve aled expression of the p105/p50 and RelA subunits of NF-kappaB, as well as the major inhibitor, I kappaB alpha, in the mammary epithelium during pregn ancy, lactation, and involution. Electrophoretic mobility shift assay (EMSA ) demonstrated that DNA-binding complexes containing p50 and RelA were abun dant during pregnancy and involution, but not during lactation. Activity of an NF-kappaB-dependent luciferase reporter in transgenic mice was highest during pregnancy, decreased to near undetectable levels during lactation, a nd was elevated during involution. This highly regulated pattern of activit y was consistent with the modulated expression of p105/p50, RelA, and I kap paB alpha. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.