Figure 1

A simplified model depicting the function of matrix-attachment regions (MARs) in gene regulation. Activation of transcription is accompanied by the anchoring of MARs to the nuclear matrix. This results in the formation of an anchored chromatin loop that is insulated from the stimulatory or repressive effects of the flanking chromatin. The transcription machinery is assembled at the site of the MAR-nuclear matrix attachments. Interaction of MARs with the nuclear matrix brings together gene coding sequences, regulatory DNA elements and the transcription machinery, thus enabling specific genes to be coordinately regulated. At the end of S phase, the replication machinery is dismantled.