The Function Of UFMylation Of PARP1 In DNA Damage Response

In the course of life,cells are inevitably exposed to various endogenous and exogenous stress that induce DNA damage, which will threaten the stability of genome and the survival of organisms. To maintain genomic stability, eukaryotic cells have evolved a series of DNA damage response (DDR) pathways. One of the fastest cellular reactions upon DINA damages is poly(ADP-ribosyl)ation (PARylation) catalysed by poly(ADP-ribose) polymerases (PA RPs). which can form poly(ADP-ribose) polymers (PAR) on acceptor proteins. Besides playing a role in DDR. PARylation plays important roles in DNA transcription and replication. cell metabolism and cell death. 17 PARP family membershave been identified so far. PARP1 executes most of PARylation activity. Ubiquitin-fold modifier l (UFMI) is a ubiquitin-like protein, UFMI is covalently attached to the receptor protein through a series of enzymatic reactions analogous to ubiquitylation, which accomplishes the modification of the target protein. This process is called UFMylati. As a post-translational modification. UFMylation plays important regulatory roles in a variety of cellular activities, such as endoplasmic reticulum homeostasis, development and differentiation of blood progenitors. In vitro. it has been found that under replication stress, PARPI is UFMylated at Lys5118, which can regulate the formation of PAR and the start of S-phase checkpoint. However, the function of UFMylation of PARP1 in vivo remains unclear.To investigate the biological significance of UFMylation of PARPI-K548, we engineered a novel PARPI point mutant mouse model named PARPI-K548R. Taking PARPI-K548R mouse embryonic fibroblasts and PARPI-K548R mice as research objects, we found that homozygous mutant mice of PARPl-K548R are found to be viable and phenotypically normal in the absence of stress. However, when cells were exposed to stress (for example, alkylating agent treatment), DNA damage accumulated and the level of PAR decreased in PARPl-K548R cells, which indicated that DDR and PARylation of PARPI-K548R cells are abnormal. As a result, PARPl-K548R cells are sensitive to alkylating DNA damage and the viability of cells is significantly reduced. We also found that PARP1-K548R1-K548R rriice are sensitive to alkylating DNA damage, which was reflected in the decrease of the depth of crypt in PARPI-K548R mice. Further research found that the proliferation of crypt cells of PARP1-K548R mice is declined and the apoptosis of crypt cells of PARP1-K548R mice is increased. Furthermore,PARP1-K548R/K548R mice are sensitive to Hydroxylurea (HU)-induced replication stress, but the detailed mechanism is still unclear.This study can help us to further understand the function of UFMylation of PARP1 in DDR,which provides a new explanation of PARP1 and its functions.