DNASE-I HYPERSENSITIVITY SITES AND NUCLEAR-PROTEIN BINDING ON THE FATTY-ACID SYNTHASE GENE - IDENTIFICATION OF AN ELEMENT WITH PROPERTIES SIMILAR TO KNOWN GLUCOSE-RESPONSIVE ELEMENTS

We have shown previously that fatty acid synthase (FAS) gene expressio n is positively regulated by glucose in rat adipose tissue and liver. In the present study, we have identified in the first intron of the ge ne a sequence closely related to known glucose-responsive elements suc h as in the L-pyruvate kinase and S14 genes, including a putative upst ream stimulatory factor/major late transcription factor (USF/MLTF) bin ding site (E-box) (+292 nt to +297 nt), Location of this sequence corr esponds to a site of hypersensitivity to DNase I which is present in t he liver but not in the spleen, Moreover, using this information from a preliminary report of the present work, others have shown that a +28 3 nt to +303 nt sequence of the FAS gene can confer glucose responsive ness to a heterologous promoter, The protein binding to this region ha s been investigated in vitro by a combination of DNase I footprinting and gel-retardation experiments with synthetic oligonucleotides and kn own nuclear proteins. DNase I footprinting experiments using a +161 nt to +405 nt fragment of the FAS gene demonstrate that a region from +2 90 nt to +316 nt is protected by nuclear extracts from liver and splee n, This region binds two ubiquitous nuclear factors, USF/MLTF and the CAAT-binding transcription factor/nuclear factor 1 (CTF/NF1). Binding of these factors is similar in nuclear extracts from liver which does or does not express the FAS gene as observed for glucose-reponsive ele ments in the L-pyruvate kinase and S14 genes, This suggests a posttran slational modification of a factor of the complex after glucose stimul ation.