Periodic transcriptional waves along the cell cycle ensure the accurate progression of the different cell cycle phases through the timely regulated expression of cell cycle proteins. The G1/S transition (Start) consists in the activation of a transcriptional program by G1 CDKs through the inactivation of Start transcriptional repressors, Whi5 and Whi7 in yeast or Rb in mammals. Here, we provide a comprehensive characterization of the transcriptional regulation of the Start repressor Whi7 in budding yeast. We found that WHI7 is a cell cycle regulated gene that shows periodic expression peaking in G1. Our results demonstrate that the three cell cycle transcriptional programs related to G1 and their corresponding transcription factors are involved in the transcriptional control of WHI7. Specifically, we identified that the transcriptional regulators Swi5 and Mcm1-Yox1, which are involved in late M and early G1 expression, and the transcription factors MBF and SBF, which are responsible for G1/S expression, are able to associate and regulate the WHI7 gene. In summary, in this work, we provide new mechanisms for the regulation of the Start repressor Whi7, which highlights the precise and complex control of the cell cycle machinery governing the G1/S transition.
Hepatocellular carcinoma (HCC), a leading cause of cancer-related death with limited therapies, is a complex disease developing in a background of Hepatitis Virus infection or systemic conditions, such as the metabolic syndrome. Investigating HCC pathogenesis in model organisms is therefore crucial for developing novel diagnostic and therapeutic tools. Genetically engineered mouse models (GEMMs) have been instrumental in recapitulating the local and systemic features of HCC. Early studies using GEMMs and patient material implicated members of the dimeric Activator Protein-1 (AP-1) transcription factor family, such as c-Jun and c-Fos, in HCC formation. In a recent report, we described how switchable, hepatocyte-restricted expression of a single-chain c-Jun~Fra-2 protein, functionally mimicking the c-Jun/Fra-2 AP-1 dimer, results in spontaneous and largely reversible liver tumors in GEMMs. Dysregulated cell cycle, inflammation, and dyslipidemia are observed at early stages and tumors display molecular HCC signatures. We demonstrate that increased c-Myc expression is an essential molecular determinant of tumor formation that can be therapeutically targeted using the BET inhibitor JQ1. Here, we discuss these findings with additional results illustrating how AP-1 GEMMs can foster preclinical research on liver diseases with novel perspectives offered by the constantly increasing wealth of HCC-related datasets.
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