Mip/LIN-9 links negative and positive transcriptional regulators critical for cell cycle progression

Cell cycle regulation is a requirement for normal cell division. It requires coordination between various negative regulators that seek to inhibit cell division and positive regulators that promote progression through the cell cycle. Without proper maintenance of this function cells are at risk for unregulated division which can lead to cell death or tumorgenesis.;Such an important mechanism requires close communication between the negative and positive regulators. Exactly how this interplay takes place is not completely understood. The pocket proteins are a major class of proteins that exert a GO arrest when they are active by inhibiting trasnscription. On the other hand, B-myb is a transcription factor that promotes S-phase and G2/Mitosis by activating transcription of genes necessary for these phases. In this thesis we show that Mip/LIN-9 acts at the interface of this process.;We hypothesis that Mip/LIN-9 plays an important role in this process. It interacts with both negative and positive regulators of the cell cycle through mutually exclusive and dynamic complexes. Formation of these complexes must be carefully balance both excessive and depleted levels of Mip/LIN-9 can interrupt proliferation. Further we show that Mip/LIN-9 exerts it ability, in part, by stabilizing the level of B-myb and promoting transcription of B-myb regulated genes.