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The super elongation complex (SEC) consists of the RNA polymerase II (Pol II) elongation factors eleven-nineteen Lys-rich leukaemia (ELL) proteins, positive transcription elongation factor b (P-TEFb) and several frequent mixed lineage leukaemia (MLL) translocation partners. The SEC controls transcription elongation in the presence or absence of promoter-proximal paused Pol II, and its gene target specificity depends on protein components forming distinct SEC complexes.
STIM proteins sense subtle changes in the levels of endoplasmice reticulum (ER)-stored Ca2+ and respond by regulating extracellular Ca2+entry and cell signalling. New structural and functional data have shed light on the role of STIM proteins as stress sensors.
Ca2+ uptake through specialized transporters allows mitochondria to act as buffers of intracellular Ca2+ levels. Moreover, mitochondrial Ca2+ signalling regulates vital processes, including metabolism and cell death. Therefore, mitochondrial Ca2+signalling remains at the epicentre of cell biological research.
Like all cell types, stem cells are subject to DNA damage, which results in the activation of checkpoint proteins, for example p53. These checkpoint responses lead to the clearance of damaged cells by cell-intrinsic and cell-extrinsic mechanisms, preventing carcinogenesis, but may also impair stem cell and tissue maintenance, thereby promoting ageing.
Forces transmitted through cell–cell and cell–extracellular matrix adhesions control cell fate decisions. But how are mechanical cues translated into gene expression programmes? The transcriptional regulators YAP and TAZ have arisen as convergence points of mechanical and biochemical signals.