The TYE7 gene of Saccharomyces cerevisiae encodes a putative bHLH‐LZ transcription factor required for Tyl‐mediated gene expression

In Saccharomyces cerevisiae , expression of a gene adjacent to the retrotransposon Ty1 is often mediated by Ty‐internal sequences. We have identified novel mutants, tye7 , which are affected in Ty1‐mediated expression of ADH2 through a Ty1 sequence distal to the 5′ long terminal repeat sequence. The TYE7 gene has been isolated and characterized. It encodes a 33 kDa protein whose N‐terminal third is extremely rich in serine residues (28%). Within its C‐terminal sequence, a remarkable similarity to Myc and Max proteins can be found. Thus, TYE7 is a potential member of the basic region/helix‐loop‐helix/leucine‐zipper protein family. TYE7 function is not essential for growth. It may primarily function as a transcriptional activator in Ty1‐mediated gene expression, as has been confirmed by the activation of reporter gene expression by a LexA‐TYE7 hybrid protein. ADH2 activation by defined Ty1 derivatives revealed that TYE7 acts positively through the more distal Ty1 enhancer element (region D), and negatively in a region between A (the 5′ proximal enhancer element) and D.