THE BETA-PHASEOLIN 5'-MATRIX ATTACHMENT REGION ACTS AS AN ENHANCER FACILITATOR

MARs found flanking the beta-phaseolin gene (phas) were tested for ins ulating activity in an enhancer blocking assay. True insulators should block enhancer dependent expression of a reporter gene when placed be tween the enhancer and a promoter. Insertion of phas 3' MAR or coding sequences lowered CaMV 35S enhancer driven GUS expression from the pha s basal promoter, indicating a distance dependence of the 35S enhancer . 5' MAR or 5' MAR core fragments could not act as independent enhance rs when fused to the phas basal promoter, and did not lower expression when inserted in the enhancer blocking assay construct, indicating th at they facilitated 35S enhancer expression at a distance when located between the enhancer and the promoter.