DISTAMYCIN PROLONGS E-SELECTIN EXPRESSION BY INTERACTING WITH A SPECIFIC NF-KAPPA-B-HMG-I(Y) BINDING-SITE IN THE PROMOTER

The E-selectin cell adhesion protein plays a critical role in mediatin g adherence of leukocytes to endothelium at sites of inflammation, Cyt okine-induced E-selectin expression on the surface of endothelial cell s is transient; mRNA expression peaks at 3-4 h after induction and ret urns to basal levels within 24 h. The mechanism for this transcription al down-modulation is not known, Promoter binding factors responsible for induced gene expression include NF-kappa B, which binds at three s ites within the E-selectin promoter, and HMG-I(Y), which binds to the A/T-rich core found at the centre of these binding sites, Distamycin i s an antibiotic that also binds A/T-rich DNA and inhibits HMG-I(Y) DNA binding, To study the role of HMG-I(Y) in E-selectin expression, we h ave examined the effect of distamycin on the cytokine-induced E-select in expression cycle, We found that distamycin prolonged E-selectin exp ression, both by sustaining mRNA transcription and by extending the tr anscript's half-life, The distamycin effect on transcription was media ted through one of the three NF-kappa B-HMG-I(Y) binding sites (NF-kap pa BII) within the promoter, This suggests that the NF-kappa B-HMG-I(Y ) complex interacting at the NF-kappa BII site plays a role not only i n cytokine induction of E-selectin expression, but also in its down-mo dulation.