Apoptosis is a genetically programmed process of cell death that is critical for embryonic development and tissue homeostasis in the adult. The BCL-2 (B-cell lymphoma 2) protein family regulates the process of apoptosis, and it contains both pro-survival and pro-apoptotic family members. BH3 (Bcl-2 homolog region [BH] 3)-only proteins (BIM, PUMA, BID, BMF, BAD, BIK, NOXA, HRK) are pro-apoptotic members of the BCL-2 protein family that are required for the initiation of apoptosis, and they play crucial roles in the killing of malignant cells by diverse anti-cancer agents. Many chemotherapeutics kill malignant cells by activation of the tumour suppressor p53. The BH3-only protein PUMA is a critical mediator of both p53-dependent and independent apoptosis and interacts with all the pro-survival BCL-2 family members (BCL-2, MCL-1, BCL-XL, A1/BFL-1, BCL-W). The absence of PUMA can accelerate tumour development and increase therapy resistance in malignant cells. In our research we aim to understand more about PUMA regulation by p53 and independently of p53 with the aim to find novel ways to boost expression of PUMA in malignant cells. We anticipate that this will increase the effectiveness of already used anti-cancer therapies. To this end we have engineered a novel reporter mouse that has the dt-Tomato gene replacing the Puma gene. This will allow us to monitor Puma gene induction in malignant as well as non-transformed cells using FACS and microscopy. We will carry out drug screens and CRISPR/Cas9 whole genome knock-out screens in these reporter cell lines to identify drugs and genes, respectively, that can regulate PUMA expression.