Transgene rescue in the mammary gland is associated with transcription but does not require translation of BLG transgenes.

Many transgenes, particularly those comprising cDNA sequences fail to be expressed when they are introduced into transgenic mice. We have previously shown that this problem can be overcome in the mammary gland by co-integrating a poorly expressed cDNA transgene, comprising the sheep beta-lactoglobulin promoter, with the efficiently expressed, unmodified beta-lactoglobulin gene. In this report we demonstrate that the transcription of the beta-lactoglobulin gene is associated with this effect because co-integration with a non-transcribed beta-lactoglobulin gene fails to rescue expression. By contrast, co-integration with a translationally inactivated beta-lactoglobulin transgene does rescue the expression of the second gene, but without the co-production of beta-lactoglobulin protein.