Identification of PARP-7 substrates reveals a role for MARylation in microtubule control in ovarian cancer cells

Abstract

PARP-7 (TiPARP) is a mono(ADP-ribosyl) transferase whose proteins substrates and biological activities are poorly understood. We observed that PARP7 mRNA levels are lower in ovarian cancer patient samples compared to non-cancerous tissue, but PARP-7 protein nonetheless contributes to several cancer-related biological endpoints in ovarian cancer cells (e.g., growth, migration). Global gene expression analyses in ovarian cancer cells subjected to PARP-7 depletion indicate biological roles for PARP-7 in cell-cell adhesion and gene regulation. To identify the MARylated substrates of PARP-7 in ovarian cancer cells, we developed an NAD+ analog-sensitive approach, which we coupled with mass spectrometry to identify the PARP-7 ADP-ribosylated proteome in ovarian cancer cells, including cell-cell adhesion and cytoskeletal proteins. Specifically, we found that PARP-7 MARylates α-tubulin to promote microtubule instability, which may regulate ovarian cancer cell growth and motility. In sum, we identified an extensive PARP-7 ADP-ribosylated proteome with important roles in cancer-related cellular phenotypes.

2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD)-Inducible Poly-ADP-Ribose Polymerase (TIPARP/PARP7) Catalytic Mutant Mice (TiparpH532A) Exhibit Increased Sensitivity to TCDD-Induced Hepatotoxicity and Lethality

“…AHR is a TIPARP substrate, but whether loss of AHR ADP-ribosylation is enough to increase sensitivity to TCDD or if there are other proteins involved is not known. Recently, chemical genetics using targeted TIPARP mutation and NAD + analogs have been used to characterize the TIPARP (PARP7) ADP-ribosylated proteome in HEK293, ovarian (OVCAR4) cancer cells and HeLa cells ( Palavalli Parsons et al , 2021 ; Rodriguez et al , 2021 ). Although metabolic targets were found among the TIPARP substrates, including the AHR target gene products ELAVL1 and SREBP1, many of the identified substrates were involved in inflammation, cell-cell adhesion and cytoskeletal signaling.…”

“…However, the most significant upregulated cellular pathways were ribosomes, RNA transport and DNA repair. The impact of TIPARP ADP-ribosylation on protein function is incompletely understood, but current data suggest that TIPARP regulates protein stability through increased ubiquitination ( Palavalli Parsons et al , 2021 ; Rodriguez et al , 2021 ). Characterizing the TCDD-induced TIPARP ADP-ribosylated proteome will be important to fully understand the increased sensitivity of Tiparp H532A mice, and may also provide new insight into TCDD-induced toxicity and wasting syndrome.…”

“…TIPARP has both cancer intrinsic effects and extrinsic effects via its inhibitory role in type I interferon (IFN) signaling, and because of this it has emerged as a potential therapeutic target for cancer treatment. TIPARP knockdown reduces ovarian cancer cell growth and motility partly through the ADP-ribosylation of α-tubulin ( Palavalli Parsons et al , 2021 ). Type I IFNs regulate tumor infiltrating immune cells and are required for an effective immune response against cancer cells, but also reduce tumor cell growth inhibition and increase apoptosis ( Musella et al , 2017 ).…”

“…Multiple studies indicate that TIPARP plays important roles in the regulation of gene expression, innate immunity, interferon signaling, and cancer ( MacPherson et al , 2013 ; Palavalli Parsons et al , 2021 ; Yamada et al , 2016 ; Zhang et al , 2020 ). TIPARP is regulated by platelet derived growth factor ( Chen et al , 2004 ), nuclear receptor family members ( Bindesboll et al , 2016 ; Kamata et al , 2021 ), hypoxia-inducible factor 1α (HIF-1α, Zhang et al , 2020 ), viral infection ( Yamada et al , 2016 ), including Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ( Heer et al , 2020 ), and the aryl hydrocarbon receptor (AHR, Ma et al , 2001 ; MacPherson et al , 2013 ).…”

Uncovering the Invisible: Mono-ADP-ribosylation Moved into the Spotlight

“…Furthermore, the enzymatic activity of ARTD10 dampened the activation of NF-κB and downstream target genes in response to interleukin-1β and TNFα, thereby potentially regulating the cancer-directed host immune responses [108]. Using chemical genetics, a recent study proposed ARTD14 to favor tumor progression in ovarian cancer [222]. Exploiting the above-described clickable NAD + analogs and a respective analog-specific ARTD14 mutant, the study identified α-tubulin as a MARylation target of ARTD14.…”