MODULATION OF AP-1 ACTIVITY BY NITRIC-OXIDE (NO) IN-VITRO - NO-MEDIATED MODULATION OF AP-1

To understand the role of nitric oxide (NO) in controlling the specifi c DNA-binding activities of transcriptional factors, we investigated t he in vitro effect of the NO-donor sodium nitroprusside (SNP) on the A P-1 activity of cultured mouse cerebellar granule cells. A gel-mobilit y assay showed that SNP inhibited AP-1 activity in the presence, but n ot the absence of dithiothreitol (DTT). This DTT-dependent inhibition of AP-1 activity by SNP corresponded with the activation of the chemic al reactivity of SNP with DTT, which can be monitored by the productio n of nitrite (NO2-). In contrast, diamide, a typical sulfhydryl oxidiz ing agent, inhibited AP-1 activity in the absence of DTT and its inhib itory effect was reversed competitively by DTT. Studies using structur ally or functionally related analogues of SNP demonstrated that S-nitr osylation of the AP-1 moiety mediated by some NO-carriers but not by f ree NO, which can be produced by the chemical reaction of SNP with DTT , was responsible for the inhibition of AP-1 activity, suggesting NO-m ediated regulation of the AP-1 transcriptional factor.