Disclosed herein are methods and means of achieving enhanced expression of a target nucleotide sequence in a transgenic organism, which methods comprise the steps of: (i) providing an organism in which post-transcriptional gene silencing (PTGS) is suppressed, (ii) associating said target nucleotide sequence with one or more heterologous Matrix Attachment Region (MARs), and (iii) causing or permitting expression from the target nucleotide sequence in the organism. Unexpectedly, the MARs do not merely relieve gene silencing, but can actually lead to expression levels higher than can be achieved in wild-type organisms and higher than expression levels in organisms in which PTGS is suppressed but where the MARs are not employed.