Travesa A, Kalashnikova T, de Bruin R, Cass SR, Chahwan C, Lee DE, Lowndes N, Wittenberg C

In Saccharomyces cerevisiae, G1/S transcription factors, MBF and SBF, regulate a large family of genes important for entry to the cell cycle and DNA replication and repair. Their regulation is crucial for cell viability and it is conserved throughout evolution. MBF and SBF consist of a common component, Swi6, and ...

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a DNA specific binding protein, Mbp1 and Swi4, respectively. Transcriptional repressors bind to and regulate the activity of both transcription factors. Whi5 binds to SBF and represses its activity at the beginning of G1 phase to prevent early activation. Nrm1 binds to MBF to repress transcription as cells progress through S phase. Here, we describe a protein motif, the "GTB motif", in Nrm1 and Whi5 that is required to bind to the transcription factors. We also identify a region of the carboxyterminus of Swi6 that is required for Nrm1 and Whi5 binding to their target transcription factors, and show that mutation of this region overrides the repression of MBF and SBF-regulated genes by Nrm1 and Whi5. Finally, we show that the GTB motif is the core of a functional module that is necessary and sufficient for targeting of the transcription factors by their cognate repressors.

Date: Feb. 04, 2013

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