Matrix attachment region regulates basal beta-lactoglobulin transgene expression

Nuclear matrix attachment regions (MAR) have been implicated in the regulation of gene expression. We have identified a region within the proximal 3'-flanking sequences of the ovine beta-lactoglobulin (betalg) gene that interacts with the nuclear matrix in vitro. No equivalent region was detected in the 5' flanking region. We have investigated the role of this element in regulating betalg expression in vitro and in vivo. Removal of the MAR did not affect the frequency of betalg transgene expression at the mRNA level, but betalg transgenes that lacked the MAR were expressed at a lower level than wild-type betalg transgenes. In neither in-vitro HC11 transfection experiments nor transgenic mice was hormonal induction of betalg expression significantly affected by MAR removal. Nuclear run-on analysis demonstrated that the impaired basal expression of betalg transgene loci lacking the MAR was due to a reduced transcription rate. Thus, the single MAR enhances the basal transcriptional potential of the betalg gene.