Project description:Ultraviolet (UV) light induces the formation of bulky UV photoproducts in the genome that interfere with DNA replication and transcription. It is well-established how human cells repair UV light-induced DNA lesions, however the signaling pathways and mechanisms that regulate transcription after exposure to UV light are poorly understood. Here, we provide a systematic view on dynamic protein phosphorylation patterns induced by UV light and uncover the dependencies of phosphorylation events on canonical DNA damage kinases and the p38 MAP kinase pathway. Notably, we demonstrate that p38 and its downstream effector kinase MK2 are responsible for one quarter of protein phosphorylation induced by UV light. We identify RNA binding proteins as primary targets and 14-3-3 family proteins as direct readers of UV light-induced, p38-MK2-dependent phosphorylation. Importantly, we demonstrate that UV light triggers rapid and dynamic phosphorylation of the negative elongation factor (NELF) complex subunit NELFE on serine 115 that mediates its binding to 14-3-3. NELFE interaction with 14-3-3 stabilizes NELFE and RNA pol II interaction on the chromatin and inhibits transcriptional elongation, thereby promoting cell survival after UV light.
Project description:Ultraviolet (UV) light induces the formation of bulky UV photoproducts in the genome that interfere with DNA replication and transcription. It is well-established how human cells repair UV light-induced DNA lesions, however the signaling pathways and mechanisms that regulate transcription after exposure to UV light are poorly understood. Here, we provide a systematic view on dynamic protein phosphorylation patterns induced by UV light and uncover the dependencies of phosphorylation events on canonical DNA damage kinases and the p38 MAP kinase pathway. Notably, we demonstrate that p38 and its downstream effector kinase MK2 are responsible for one quarter of protein phosphorylation induced by UV light. We identify RNA binding proteins as primary targets and 14-3-3 family proteins as direct readers of UV light-induced, p38-MK2-dependent phosphorylation. Importantly, we demonstrate that UV light triggers rapid and dynamic phosphorylation of the negative elongation factor (NELF) complex subunit NELFE on serine 115 that mediates its binding to 14-3-3. NELFE interaction with 14-3-3 stabilizes NELFE and RNA pol II interaction on the chromatin and inhibits transcriptional elongation, thereby promoting cell survival after UV light.
Project description:Ultraviolet (UV) light radiation induces the formation of bulky photoproducts in the DNA that globally affect transcription and splicing. However, the signaling pathways and mechanisms that link UV light-induced DNA damage to changes in RNA metabolism remain poorly understood. Here, we employ quantitative phosphoproteomics and protein kinase inhibition to provide a systems view on protein phosphorylation patterns induced by UV light, and uncover the dependencies of phosphorylation events on the canonical DNA damage signaling by ATM/ATR and the p38 MAP kinase pathway. We identify RNA binding proteins as primary substrates and 14-3-3 as direct readers of p38-MK2-dependent phosphorylation induced by UV light. Mechanistically, we show that MK2 phosphorylates the RNA binding subunit of the NELF complex NELFE on Serine 115. NELFE phosphorylation promotes the recruitment of 14-3-3 and rapid dissociation of the NELF complex from chromatin, which is accompanied by RNA polymerase II elongation.
Project description:Ultraviolet (UV) light radiation induces the formation of bulky photoproducts in the DNA that interfere with replication and transcription. Recent studies showed that exposure of human cells to UV light globally affects transcription and alternative splicing, however, the signaling pathways and mechanisms that link UV light-induced DNA damage to RNA metabolism regulation remain poorly understood. Here, we provide a systems view on protein phosphorylation patterns induced by UV light, and uncover the dependencies of phosphorylation events on the canonical DNA damage signaling mediated by ATM/ATR or p38 MAP kinase pathway. We identify RNA binding proteins as primary targets and 14-3-3 family as direct readers of p38-MK2-dependent phosphorylation induced by UV light. Moreover, we show that MK2 phosphorylates the RNA binding subunit of the NELF complex NELFE on S115. NELFE phosphorylation promotes the recruitment of 14-3-3 and rapid dissociation of the NELF complex from chromatin that is accompanied with an increase in transcriptional elongation.
Project description:SUMOylation is a posttranslational protein modification which is characterized by the covalent attachment of a small 11kDa protein, called Small Ubiquitin-like MOdifier (SUMO). SUMOylation plays a pivotal role in a multitude of cellular pathways including cellular responses upon DNA damage. Here, we identified multiple proteins which are SUMOylated in U2OS cells in response to ultraviolet light (UV) irradiation and ionizing radiation (IR). We show that the SUMOylation response upon UV irradiation was more pronounced compared to the response upon IR. The major SUMOylation target upon UV-irradiation was the transcription-coupled nucleotide excision repair (TC-NER) protein, Cockayne Syndrome B (CSB). This protein plays an important role in the repair of UV-induced lesions in actively transcribed genes. In a second proteomic approach we identified SUMOylation-dependent and independent protein interactors of the N-terminus of CSB. Here, we uncovered that the affinity of multiple RNA polymerase-associated proteins towards CSB is influenced by SUMOylation. Finally, we set out to identify ubiquitination events upon UV-irradiation which are influenced by the CSA-ubiquitin ligase complex, which is also involved in TC-NER and is closely connected to CSB, because mutations in either CSA or CSB result in the same phenotype, Cockayne syndrome. We found that RPB1, the major subunit of RNA polymerase II, was ubiquitinated in a CSA-dependent manner upon UV which finally led to its degradation.