Poly(ADP-ribosyl)ating pathway regulates development from stem cell niche to longevity control.

Guillaume Bordet,Alexei V Tulin,Elena Kotova

doi:10.26508/lsa.202101071

Guillaume Bordet, Alexei V Tulin + Show 1 more

Open Access

https://doi.org/10.26508/lsa.202101071

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Abstract

The regulation of poly(ADP-ribose) polymerase, the enzyme responsible for the synthesis of homopolymer ADP-ribose chains on nuclear proteins, has been extensively studied over the last decades for its involvement in tumorigenesis processes. However, the regulation of poly(ADP-ribose) glycohydrolase (PARG), the enzyme responsible for removing this posttranslational modification, has attracted little attention. Here we identified that PARG activity is partly regulated by two phosphorylation sites, ph1 and ph2, in Drosophila We showed that the disruption of these sites affects the germline stem-cells maintenance/differentiation balance as well as embryonic and larval development, but also the synchronization of egg production with the availability of a calorically sufficient food source. Moreover, these PARG phosphorylation sites play an essential role in the control of fly survivability from larvae to adults. We also showed that PARG is phosphorylated by casein kinase 2 and that this phosphorylation seems to protect PARG protein against degradation in vivo. Taken together, these results suggest that the regulation of PARG protein activity plays a crucial role in the control of several developmental processes.

Highlights

Poly(ADP-ribose) polymerase 1 (PARP-1) uses NAD as a substrate to synthesize poly(ADP-ribose) polymer on the surface of nuclear proteins [1] (Fig 1A)
Among all possible phosphorylated peptides, we found only peptides corresponding to ph1 and ph2 sites, which perfectly match those previously reported in Drosophila phospho-proteome studies, excepted for T623 that we did not detect phosphorylated [27] (Fig 2B and Table S2)
When we compared the effects of PARGWT (Fig S7C and D), PARGSA and PARGSE on parg27.1 mutants on germline stem cells maintenance and differentiation, we found that the phospho-mutant poly(ADP-ribose) glycohydrolase (PARG) isoform PARGSA shows a sharp increase in the number of roundshaped fusome-positive cells, up to five, on average (Fig 4E and F), whereas the parg27.1 mutant expressing either PARGWT or PARGSE shows no significant difference (Fig 4C, D, and F)

Summary

Introduction

Poly(ADP-ribose) polymerase 1 (PARP-1) uses NAD as a substrate to synthesize poly(ADP-ribose) polymer (pADPr) on the surface of nuclear proteins [1] (Fig 1A). The poly(ADP-ribosyl)ation pathway regulates many nuclear functions, including DNA repair, chromatin structure, and transcription initiation, as well as pre-mRNA fate, via alternative splicing [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], by altering the physical and enzymatic properties of acceptor proteins, which, owing to the presence of poly(ADP-ribose) phosphate moieties, become highly negatively charged and dissociate from their target nucleic acids [1, 2] (Fig 1A). Antagonistic effects of PARP-1 and PARG on pADPr are reflected in their distinct intracellular localization (Fig 1C), which may explain the timing of changes in poly(ADP-ribose) levels during the cell cycle. The effects of phosphorylation on PARG function in mammals or Drosophila remain unclear

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