PARP-2 sustains erythropoiesis in mice by limiting replicative stress in erythroid progenitors

Abstract

Erythropoiesis is a tightly regulated process in which multipotential hematopoietic stem cells produce mature red blood cells. Here we show that deletion of poly(ADP-ribose) polymerase-2 (PARP-2) in mice leads to chronic anemia at steady state, despite increased erythropoietin plasma levels, a phenomenon not observed in mice lacking PARP-1. Loss of PARP-2 causes shortened lifespan of erythrocytes and impaired differentiation of erythroid progenitors. In erythroblasts, PARP-2 deficiency triggers replicative stress, as indicated by the presence of micronuclei, the accumulation of γ-H2AX (phospho-histone H2AX) in S-phase cells and constitutive CHK1 and replication protein A phosphorylation. Transcriptome analyses revealed the activation of the p53-dependent DNA-damage response pathways in PARP-2-deficient cells, culminating in the upregulation of cell-cycle and cell death regulators, concomitant with G2/M arrest and apoptosis. Strikingly, while loss of the proapoptotic p53 target gene Puma restored hematocrit levels in the PARP-2-deficient mice, loss of the cell-cycle regulator and CDK inhibitor p21 leads to perinatal death by exacerbating impaired fetal liver erythropoiesis in PARP-2-deficient embryos. Although the anemia displayed by PARP-2-deficient mice is compatible with life, mice die rapidly when exposed to stress-induced enhanced hemolysis. Our results pinpoint an essential role for PARP-2 in erythropoiesis by limiting replicative stress that becomes essential in the absence of p21 and in the context of enhanced hemolysis, highlighting the potential effect that might arise from the design and use of PARP inhibitors that specifically inactivate PARP proteins.

Targeting the kinase activities of ATR and ATM exhibits antitumoral activity in mouse models of MLL -rearranged AML

“…Moreover, recent reports have shown good efficacy of ATR or CHK1 inhibitors in hematopoietic tumors, mostly in in vitro settings (6–11). The particular efficacy of RSR inhibitors in lymphoid tumors is consistent with a preferential role for the RSR in the untransformed lymphoid compartment, exemplified by the frequent presence of anemia in mice suffering from RS (13, 24–27). Overall, these analyses identify distinctively high levels of CHEK1 expression in lymphomas and leukemias, which could be indicative of underlying DNA replication stress.…”

“…Second, inhibitors of ATR or its target CHK1 are toxic for several lymphomas and leukemias, including p53-deficient tumors (6–9, 11, 23). Moreover, the particular efficacy of RSR inhibitors in lymphoid tumors is consistent with a preferential role for the RSR in the untransformed lymphoid compartment, exemplified by the frequent presence of anemia in mice suffering from DNA replication stress (13, 24–27). Finally, inhibition of ATR or inhibition of the related DNA damage response (DDR) kinase ATM predisposed primary stem cells infected with retroviruses expressing MLL-AF9, a fusion between the KMT2A and the transcription activator AF9, towards differentiation in vitro (28).…”

Biology of Poly(ADP-Ribose) Polymerases: The Factotums of Cell Maintenance

“…These studies revealed that PARP inhibition impacts on the differentiation of bone-marrow-derived cells (monocyte/macrophage, erythroid, or neutrophil and B cell lineages), neurons, spermatocytes, skeletal muscle, osteoblasts, and adipocytes (Virá g and Szabó , 2002). Later studies not only verified these results, but also extended them by implicating other PARP enzymes (e.g., PARP-2) in differentiation (Farré s et al, 2014;Szá ntó et al, 2012). The PARP-regulated molecular pathways in the regulation of differentiation are not fully elucidated; nonetheless, changes in chromatin structure, gene expression, mitochondrial activity, metabolism, and cell death are involved.…”

PARP and PARG inhibitors in cancer treatment

“…6). This leads to an accumulation of DNA damage in S-phase cells, S-phase stalling, and G2 delay (Sugimura et al 2008;Bryant et al 2009;Ray Chaudhuri et al 2012;Berti et al 2013;Dale Rein et al 2015;Farrés et al 2015;Maya-Mendoza et al 2018;Michelena et al 2018;Ronson et al 2018). In PARP1-depleted or inhibited cells, DSBs arise due to deprotection of stalled replication forks and their degradation by the MRE11 nuclease, due to impaired fork reversal, or from unligated Okazaki fragments encountered by replication forks (Lonn and Lonn 1985;Ray Chaudhuri et al 2012;Ying et al 2012;Hanzlikova et al 2018).…”