Biology subjects

Shapira, D.

Publications and source records attributed to Shapira, D..

2 recordsLinked to original sources

bioRxiv2025

RIF1 orchestrates a multi-step restoration of post-replicative H3K9me3

DNA replication causes the dilution of parental histones along with their specific post-translational modifications. The kinetics of restoring these marks on newly incorporated histones dictate how quickly genomic domains regain their epigenetic identity after replication. H3K9me3 is restored extremely slowly; the process of reconstitution, to achieve the pre-replication levels, continues throughout the following G1 phase. The molecular mechanisms behind this slow reconstitution are unknown. We show here that RIF1s reassociation with heterochromatin during mitotic exit is required to set up a chromatin environment permissive for histone methyltransferases to resume H3K9me3 deposition. RIF1 facilitates the recruitment of SUV39H1, HP1 and HP1{beta} and is required for the increased tri-methylation of H3K9 that occurs during G1 phase. RIF1 is also indispensable for recruiting Protein Phosphatase 1 (PP1) to heterochromatin, and the interaction between RIF1 and PP1 is essential for the maintenance of H3K9me3 levels. In addition, RIF1-PP1 complex temporally restrains the activity of Aurora kinase at heterochromatin, ensuring that phosphorylation of H3S10 does not precede replication. This creates a time- window permissive for SUV39Hs to initiate the reinstatement of H3K9me3.

cell biology↗

bioRxiv2020

Autophagy promotes cell and organismal survival by maintaining NAD(H) pools

Autophagy is an essential catabolic process that promotes clearance of surplus or damaged intracellular components1. As a recycling process, autophagy is also important for the maintenance of cellular metabolites during periods of starvation2. Loss of autophagy is sufficient to cause cell death in animal models and is likely to contribute to tissue degeneration in a number of human diseases including neurodegenerative and lysosomal storage disorders3-7. However, it remains unclear which of the many cellular functions of autophagy primarily underlies its role in cell survival. Here we have identified a critical role of autophagy in the maintenance of nicotinamide adenine dinucleotide (NAD+/NADH) levels. In respiring cells, loss of autophagy caused NAD(H) depletion resulting in mitochondrial membrane depolarisation and cell death. We also found that maintenance of NAD(H) is an evolutionary conserved function of autophagy from yeast to human cells. Importantly, cell death and reduced viability of autophagy-deficient animal models can be partially reversed by supplementation with an NAD(H) precursor. Our study provides a mechanistic link between autophagy and NAD(H) metabolism and suggests that boosting NAD(H) levels may be an effective intervention strategy to prevent cell death and tissue degeneration in human diseases associated with autophagy dysfunction.

cell biology↗