PARP1 mediates poly-ADP-ribosylation of proteins on chromatin in response to different types of DNA lesions. PARP inhibitors are used for the treatment of BRCA1/2-deficient breast, ovarian, and prostate cancer. Loss of DNA replication fork protection is proposed as one mechanism that contributes to the vulnerability of BRCA1/2-deficient cells to PARP inhibitors. However, the mechanisms that regulate PARP1 activity at stressed replication forks remain poorly understood. Here, we performed proximity proteomics of PARP1 and isolation of proteins on stressed replication forks to map putative PARP1 regulators. We identified TPX2 as a direct PARP1-binding protein that regulates the auto-ADP-ribosylation activity of PARP1. TPX2 interacts with DNA damage response proteins and promotes homology-directed repair of DNA double-strand breaks. Moreover, TPX2 mRNA levels are increased in BRCA1/2-mutated breast and prostate cancers, and high TPX2 expression levels correlate with the sensitivity of cancer cells to PARP-trapping inhibitors. We propose that TPX2 confers a mitosis-independent function in the cellular response to replication stress by interacting with PARP1.
Kinase fusions are considered oncogenic drivers in numerous types of cancer. In lung adenocarcinoma 5-10% of patients harbor kinase fusions. The most frequently detected kinase fusion involves the Anaplastic Lymphoma Kinase (ALK) and Echinoderm Microtubule-associated protein-Like 4 (EML4). In addition, oncogenic kinase fusions involving the tyrosine kinases RET and ROS1 are found in smaller subsets of patients. In this study, we employed quantitative mass spectrometry-based phosphoproteomics to define the cellular tyrosine phosphorylation patterns induced by different oncogenic kinase fusions identified in patients with lung adenocarcinoma. We show that exogenous expression of the kinase fusions in HEK 293T cells leads to widespread tyrosine phosphorylation. Direct comparison of different kinase fusions demonstrates that the kinase part and not the fusion partner primarily defines the phosphorylation pattern. The tyrosine phosphorylation patterns differed between ALK, ROS1, and RET fusions, suggesting that oncogenic signaling induced by these kinases involves the modulation of different cellular processes.
With increasing demands for inquiry-competent problem-solvers and emerging evidence that active problem-solving promotes a deeper understanding of science (1-3), universities are facing a need to rethink teaching styles to promote students as active contributors to exploring and solving scientific problems (4, 5). One way is through integrating research in teaching. This method involves a dynamic process of realization for both the student and the researcher and is centered around a scientific area of interest to both (6). In a course on intrinsically disordered proteins (IDPs) (7), we explored how teaching and research can be integrated in ways that not only confer deep learning (8) and research-related skills, but also create new scientific insights.IDPs are a group of recently discovered proteins. Unlike other proteins, the function of IDPs is not tied to a three-dimensional form. Instead, they exist as dynamic ensembles of disordered structures relevant to their function. The disordered dynamics and discord of function from a specific shape challenges a .60-yr-old paradigm (9) that has shaped the established scientific knowledge on what proteins look like and how they function (10-12) (Fig 1a). IDPs are not an oddity but make up 30-40% of the human genome (13) with key roles in health and disease (14). They are subject to an emerging interest, not only in basic research (15,16), but also from industries, having an interest in their roles in diseases and cures and in using them as novel biomaterials. The limited knowledge and potential for important
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