CHARACTERIZATION OF A TRANSCRIPTIONAL CONTROL ELEMENT INVOLVED IN PROLIFERATION OF PEROXISOMES IN YEAST IN RESPONSE TO OLEATE

Oleate induces the transcription of genes involved in peroxisome bioge nesis and stimulates the proliferation of these organelles in Saccharo myces cerevisiae. Previously, we have reported the identification of a region containing a positive regulatory element in the 5' flanking re gion of the FOX3 gene encoding the peroxisomal enzyme 3-oxoacyl-CoA th iolase. This region contains a 23-bp imperfect inverted-repeat sequenc e. Full induction, in response to oleate, is mediated by the intact dy ad. However, one half-site of the inverted repeat is also able to medi ate induction of transcription in response to oleate, albeit to a smal l extent. Furthermore, the weak binding of protein to each part of the inverted repeat proved to be correlated with the weak activation of t ranscription, in support of oleate. A DNase-I footprint covered the en tire dyad and DNA band-shift experiments indicated that one or more tr ans-acting factors bind to the imperfect palindrome. The binding of pr otein to this element seems to be correlated with transcriptional acti vation, since mutations in both halves of the inverted dyad affected b oth transcriptional activation and protein binding in vitro. Similar o leate-responsive elements are commonly found in the 5' flanking region s of genes encoding proteins involved in peroxisome biogenesis and the factor(s) binding to oleate-responsive element(s) could therefore be involved in coordination of the expression of oleate-inducible genes a nd the proliferation of peroxisomes.