PubMed · 11135660
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W T Miller. 2001. Double trouble.. https://doi.org/10.1038/82986
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The human mitochondrial genome must be replicated and expressed in a timely manner to maintain energy metabolism and supply cells with adequate levels of adenosine triphosphate. Central to this process is the idea that replication primers and gene products both arise via transcription from a single light strand promoter (LSP) such that primer formation can influence gene expression, with no consensus as to how this is regulated. Here, we report the discovery of a second light strand promoter (LSP2) in humans, with features characteristic of a bona fide mitochondrial promoter. We propose that the position of LSP2 on the mitochondrial genome allows replication and gene expression to be orchestrated from two distinct sites, which expands our long-held understanding of mitochondrial gene expression in humans.
Small-molecule kinase inhibitors represent a major group of cancer therapeutics, but tumor responses are often incomplete. To identify pathways that modulate kinase inhibitor response, we conducted a genome-wide knockout (KO) screen in glioblastoma cells treated with the pan-ErbB inhibitor neratinib. Loss of general control nonderepressible 2 (GCN2) kinase rendered cells resistant to neratinib, whereas depletion of the GADD34 phosphatase increased neratinib sensitivity. Loss of GCN2 conferred neratinib resistance by preventing binding and activation of GCN2 by neratinib. Several other Food and Drug Administration (FDA)-approved inhibitors, such erlotinib and sunitinib, also bound and activated GCN2. Our results highlight the utility of genome-wide functional screens to uncover novel mechanisms of drug action and document the role of the integrated stress response (ISR) in modulating the response to inhibitors of oncogenic kinases.
Protein kinases play a central role in cellular signal transduction, by transmitting biochemical information between activated membrane-bound receptors and physiological target proteins. In addition to phosphorylating other proteins, almost all protein kinases catalyse autophosphorylation reactions (i.e. reactions in which the kinase serves as its own substrate). The autophosphorylation reactions can be intramolecular or intermolecular. In the present study, a detailed kinetic analysis of the intermolecular autophosphorylation reaction is presented. On the basis of the kinetic equations, a new procedure is developed to evaluate the kinetic parameters of the autophosphorylation reaction. This method was used to analyse the intermolecular autophosphorylation of an S6/H4 kinase from human placenta. At a fixed ATP concentration of 0.125 mM, the apparent catalytic-centre activity (turnover number; k (cat)) and apparent Michaelis-Menten constant ( K (m)) for the autophosphorylation reaction were determined to be 0.91 min(-1) and 0.86 microM respectively.