[Activation of a trans-activating factor of NF1 transcription in a lactating mammary gland].

Functional differentiation of a bovine mammary gland in the course of lactation is characterized by significant increase of tissue-specific expression of genes encoding milk proteins (caseins, lactoglobulin etc.). The NF1 is known as a ubiquitous transcription factor which modulates a tissue-specific transcription of different genes (including beta-casein) cooperating with tissue-specific and other ubiquitous transcription factors. We have observed a dramatic increase of NF1-binding activity in nuclear extracts of bovine mammary gland during lactation. The NF1 transcription factor appears to have a cytoplasmic precursor pool. This cytoplasmic precursor as well as NF-kappa B cytoplasmic precursor could be activated in vitro by deoxycholate (DOC) treatment which caused possibly dissociation of a complex of NF1 and its cytoplasmic inhibitor. There was an inverse proportion between concentrations of active nuclear NF1 factor and its cytoplasmic precursor. We have observed an increase of nuclear factor binding and a simultaneous decrease of the cytoplasmic precursor pool in the course of lactation. We have determined the NF1 protein subunit composition using UV-cross-linking 32P labeled NF1-oligonucleotide with nuclear and cytoplasmic proteins of mammary gland. The main subunits of NF1 factor were p50 and p20. The drastic increase of nuclear NF1 binding activity was correlated with significant increase of the p20 subunit concentration in nuclear protein during lactation.