PARP1 Regulates the Biogenesis and Activity of Telomerase Complex Through Modification of H/ACA-Proteins.

Nikita V Savelyev,Nikita M Shepelev,Maria P Rubtsova,Olga I Lavrik,Olga A Dontsova

doi:10.3389/fcell.2021.621134

Abstract

Poly(ADP-ribose) polymerase 1 (PARP1) is established as a key regulator of the cellular DNA damage response and apoptosis. In addition, PARP1 participates in the global regulation of DNA repair, transcription, telomere maintenance, and inflammation response by modulating various DNA-protein and protein-protein interactions. Recently, it was reported that PARP1 also influences splicing and ribosomal RNA biogenesis. The H/ACA ribonucleoprotein complex is involved in a variety of cellular processes such as RNA maturation. It contains non-coding RNAs with specific H/ACA domains and four proteins: dyskerin (DKC1), GAR1, NHP2, and NOP10. Two of these proteins, DKC1 and GAR1, are targets of poly(ADP-ribosyl)ation catalyzed by PARP1. The H/ACA RNA-binding proteins are involved in the regulation of maturation and activity of the telomerase complex, which maintains telomere length. In this study, we demonstrated that of poly(ADP-ribosyl)ation influences on RNA-binding properties of DKC1 and GAR1 and telomerase assembly and activity. Our data provide the evidence that poly(ADP-ribosyl)ation regulates telomerase complex assembly and activity, in turn regulating telomere length that may be useful for design and development of anticancer therapeutic approaches that are based on the inhibition of PARP1 and telomerase activities.

Highlights

Post-translational modifications regulate the localization, stability, and activity of proteins, thereby allowing the transformation of cellular signals into biological outcomes
A global analysis of ADP-ribosylation revealed that the components of the H/ACA-complex (Zhang et al, 2013), DKC1 and GAR1, are targets of PARylation, and we decided to investigate the pattern of H/ACA RNA binding to PARylated and nonPARylated mutant forms of these proteins
We concluded that introduced mutations prevent the PARylation of GAR1 and DKC1 that results in the decreased molecular weight of proteins that was observed by western blotting (Figures 1C,D)

Summary

Introduction

Post-translational modifications regulate the localization, stability, and activity of proteins, thereby allowing the transformation of cellular signals into biological outcomes. PARP1 or poly(ADPribose) polymerase 1 catalyzes the covalent synthesis of the long branched polymer, poly(ADPribose) (PAR), utilizing nicotinamide adenine nucleotide (NAD+) as a substrate (Amé et al, 2004; Langelier et al, 2018) This reaction is reversible, as PAR is quickly hydrolyzed by poly(ADPribose) glycohydrolase (PARG) (Amé et al, 2004; Pascal and Ellenberger, 2015). PARG is an abundant enzyme that degrades PAR by a combination of endo- and exo-glycohydrolase activity, removing most of the PAR polymer but leaving behind a single ADP-ribose attached to the protein This remnant ADP-ribosyl modification can be removed by mono-(ADP-ribose) glycohydrolases (Oka et al, 2006; Han et al, 2011; Kato et al, 2011). PARP1 functions in the global regulation of transcription (Frizzell et al, 2009), telomere maintenance (Tong et al, 2001; Espejel et al, 2004; Blasco, 2005; Beneke et al, 2008; Hoang et al, 2020), and inflammatory response (Francis et al, 1983; Bai et al, 2009)

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Results

Conclusion