Regulation of ovine beta-lactoglobulin gene expression during the first stage of lactogenesis.

In the lactating mammary gland, expression of the ovine beta-lactoglobulin gene correlates with the presence of a strong DNaseI hypersensitive site encompassing the promoter region. At this stage of lactogenesis, prolactin is required for optimal expression. Using DNaseI as a probe for formation of a transcription complex on the beta-lactoglobulin promoter, the temporal pattern of ovine beta-lactoglobulin expression during pregnancy has been addressed. The appearance of nuclease hypersensitivity during pregnancy correlates with rising levels of placental lactogen which suggests that this hormone may be the stimulus for expression during the first stage of lactogenesis. This raises the possibility that a different signalling pathway to that present in the lactation functions during pregnancy.