A SACCHAROMYCES-CEREVISIAE MITOCHONDRIAL-DNA FRAGMENT ACTIVATES REG1P-DEPENDENT GLUCOSE-REPRESSIBLE TRANSCRIPTION IN THE NUCLEUS

As part of an effort to identify random carbon-source-regulated promot ers in the Saccharomyces cerevisiae genome, we discovered that a mitoc hondrial DNA fragment is capable of directing glucose-repressible expr ession of a reporter gene. This fragment (CR24) originated from the mi tochondrial genome adjacent to a transcription initiation site. Mutati onal analyses identified a GC cluster within the fragment that is requ ired for transcriptional induction. Repression of nuclear CR24-driven transcription required Reg1p, indicating that this mitochondrially der ived promoter is a member of a large group of glucose-repressible nucl ear promoters that are similarly regulated by Reg1p. In vivo and in vi tro binding assays indicated the presence of factors, located within t he nucleus and the mitochondria, that bind to the GC cluster. One or m ore of these factors may provide a regulatory link between the nucleus and mitochondria.