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McQuaid, M.

Publications and source records attributed to McQuaid, M..

3 recordsLinked to original sources

Overexpression of AMPKγ2 increases AMPK signaling to augment human T cell metabolism and function

T cell-based cellular therapies benefit from a product with reduced differentiation and enhanced oxidative metabolism. Methods to achieve this balance without negatively impacting T cell expansion or impairing T cell function have proven elusive. AMP-activated protein kinase (AMPK) is a cellular energy sensor which promotes mitochondrial health and improves oxidative metabolism. We hypothesized that increasing AMPK activity in human T cells would augment their oxidative capacity, creating an ideal product for adoptive cellular therapies. Lentiviral transduction of the regulatory AMPK{gamma}2 subunit stably enhanced intrinsic AMPK signaling and promoted mitochondrial respiration with increased basal oxygen consumption rates (OCR), higher maximal OCR, and augmented spare respiratory capacity. These changes were accompanied by increased mitochondrial density and elevated expression of proteins involved in mitochondrial fusion. AMPK{gamma}2-transduction also increased T cell glycolytic activity. This combination of metabolic reprogramming enhanced in vitro T cell expansion while promoting memory T cell yield. Finally, when activated under decreasing glucose conditions, AMPK{gamma}2-transduced T cells maintained higher levels of both proliferation and inflammatory cytokine production. Together, these data suggest that augmenting intrinsic AMPK signaling via overexpression of AMPK{gamma}2 can improve the expansion and function of human T cells for subsequent use in adoptive cellular therapies. Key pointsLentiviral Transduction of AMPK{gamma}2 increases oxidative metabolism in human T cells AMPK{gamma}2 transduction enhances in vitro proliferation without inducing exhaustion AMPK{gamma}2-transduced T cells function better under low glucose conditions

immunology↗

Persistent acetylation of newly synthesized histones inhibits DNA replication origin activity

In Saccharomyces cerevisiae, newly synthesized histone H3 are acetylated on lysine 56 (H3 K56ac) by the Rtt109 acetyltransferase prior to their deposition on nascent DNA behind replication forks. Two deacetylases of the sirtuin family, Hst3 and Hst4, remove H3 K56ac from chromatin following S phase. hst3{Delta} hst4{Delta} cells present constitutive H3 K56ac, which sensitizes cells to replicative stress via mechanisms that remain unclear. We performed a screen to identify genes that influence cell fitness upon nicotinamide (NAM)-induced inhibition of sirtuins. The screen revealed that DBF4 heterozygosity causes NAM sensitivity. DBF4 and CDC7 encode subunits of the Dbf4-dependent kinase, which activates origins of DNA replication. We show that i) cells harboring the dbf4-1 or cdc7-4 hypomorphic alleles are sensitive to NAM, ii) Rif1, an inhibitor of Cdc7-dependent activation of origins, causes DNA damage and replication defects in NAM-treated cells and hst3{Delta} hst4{Delta} mutants, and iii) cdc7-4 hst3{Delta} hst4{Delta} cells display synthetic temperature sensitivity associated with delayed initiation of DNA replication. Such replication defects are not due to activation of the intra-S phase checkpoint but require Rtt109-dependent H3 K56ac. Overall, these results suggest that persistent H3 K56ac sensitizes cells to replicative stress in part by negatively influencing replication origin activity.

molecular biology↗

A genome-wide screen identifies SCAI as a modulator of the UV-induced replicative stress response in human cells

Helix-destabilizing DNA lesions induced by environmental mutagens such as UV light cause genomic instability by strongly blocking the progression of DNA replication forks (RF). At blocked RF, single-stranded DNA (ssDNA) accumulates and is rapidly bound by Replication Protein A (RPA) complexes. Such stretches of RPA-ssDNA constitute platforms for recruitment/activation of critical factors that promote DNA synthesis restart. However, during periods of severe replicative stress, RPA availability may become limiting due to inordinate sequestration of this multifunctional complex on ssDNA, thereby negatively impacting multiple vital RPA-dependent processes. Here, we performed a genome-wide screen to identify factors which restrict the accumulation of RPA-ssDNA during UV-induced replicative stress. While this approach revealed some expected "hits" acting in pathways such as nucleotide excision repair, translesion DNA synthesis, and the intra-S phase checkpoint, it also identifed SCAI, whose role in the replicative stress response was previously unappreciated. Upon UV exposure, SCAI knock-down caused elevated accumulation of RPA-ssDNA during S phase, accompanied by reduced cell survival and compromised RF progression. These effects were independent of the previously reported role of SCAI in 53BP1-dependent DNA double-strand break repair. We also found that SCAI colocalized with stalled RF, and that its depletion promoted nascent DNA degradation. Finally, we (i) provide evidence that EXO1 is the major nuclease underlying ssDNA formation and consequent DNA replication defects in SCAI knockout cells and, consistent with this, (ii) demonstrate that SCAI inhibits EXO1 activity on a ssDNA gap in vitro. Taken together, our data establish SCAI as a novel regulator of the replicative stress response in human cells.

molecular biology↗