ARTC1-mediated VAPB ADP-ribosylation regulates calcium homeostasis

Mono-ADP-ribosylation(MARylation)is a post-translational modification that regulates a variety of biological processes,including DNA damage repair,cell proliferation,metabolism,and stress and immune responses.In mammals,MARylation is mainly catalyzed by ADP-ribosyltransferases(ARTs),which consist of two groups:ART cholera toxin-like(ARTCs)and ART diphtheria toxin-like(ARTDs,also known as PARPs).The human ARTC(hARTC)family is composed of four members:two active mono-ADP-ARTs(hARTC1 and hARTC5)and two enzymatically inactive enzymes(hARTC3 and hARTC4).In this study,we systematically examined the homology,expression,and localization pattern of the hARTC family,with a particular focus on hARTC1.Our results showed that hARTC3 interacted with hARTC1 and promoted the enzymatic activity of hARTC1 by stabilizing hARTC1.We also identified vesicle-associated membrane protein-associated protein B(VAPB)as a new target of hARTC1 and pinpointed Arg50 of VAPB as the ADP-ribosylation site.Furthermore,we demonstrated that knockdown of hARTC1 impaired intracellular calcium homeostasis,highlighting the functional importance of hARTC1-mediated VAPB Arg50 ADP-ribosylation in regulating calcium homeostasis.In summary,our study identified a new target of hARTC1 in the endoplasmic reticulum and suggested that ARTC1 plays a role in regulating calcium signaling.

Distinct roles of ASIC3 and TRPV1 receptors in electroacupuncture-induced segmental and systemic analgesia

Previous studies have demonstrated the effects of different afferent fibers on electroacupuncture （EA）- induced analgesia. However, contributions of functional receptors expressed on afferent fibers to the EA analgesia remain unclear. This study investigates the roles of acid-sensing ion channel 3 （ASIC3） and transient receptor potential vanifioid 1 （TRPV1） receptors in EA-induced segmental and systemic analgesia. Effects of EA at acupoint ST36 with different intensities on the C-fiber reflex and mechanical and thermal pain thresholds were measured among the ASIC3-/-, TRPV1-/-, and C57BL/6 mice. Compared with C57BL/6 mice, the ipsilateral inhibition of EA with 0.8 C-fiber threshold （0.8Tc） intensity on C-fiber reflex was markedly reduced in ASIC3-/- mice, whereas the bilateral inhibition of 1.0 and 2.0Tc EA was significantly decreased in TRPV1-/- mice. The segmental increase in pain thresholds induced by 0.3 mA EA was significantly reduced in ASIC3-/- mice, whereas the systemic enhancement of 1.0 mA EA was markedly decreased in TRPV1-/- mice. Thus, segmental analgesia of EA with lower intensity is partially mediated by ASIC3 receptor on Aβ-fiber, whereas systemic analgesia induced by EA with higher intensity is more likely induced by TRPV1 receptor on Aδ- and C-fibers.

The role of BRCA1 in DNA damage response

BRCA1 is a well-established tumor suppressor gene,which is frequently mutated in familial breast and ovarian cancers.The gene product of BRCA1 functions in a number of cellular pathways that maintain genomic stability,including DNA damage-induced cell cycle checkpoint activation,DNA damage repair,protein ubiquitination,chromatin remodeling,as well as transcriptional regulation and apoptosis.In this review,we discuss recent advances regarding our understanding of the role of BRCA1 in tumor suppression and DNA damage response,including DNA damage-induced cell cycle checkpoint activation and DNA damage repair.

The RNF20/40 complex regulates p53-dependent gene transcription and mRNA splicing

p53 is a key transcription factor to regulate gene transcription.However,the molecular mechanism of chromatin-associated p53 on gene transcription remains elusive.Here,using unbiased protein affinity purification,we found that the RNF20/40 complex associated with p53 on the chromatin.Further analyses indicated that p53 mediated the recruitment of the RNF20/40 complex to p53 target gene loci including p21 and PUMA loci and regulated the transcription of p21 and PUMA via the RNF20/40 complex-dependent histone H2B ubiquitination(ubH2B).Lacking the RNF20/40 complex suppressed not only ubH2B but also the generation of the mature mRNA of p21 and PUMA.Moreover,ubH2B was recognized by the ubiquitin-binding motif of pre-mRNA processing splicing factor 8(PRPF8),a subunit in the spliceosome,and PRPF8 was required for the maturation of the mRNA of p21 and PUMA.Our study unveils a novel p53-dependent pathway that regulates mRNA splicing for tumor suppression.

Functions of PARylation in DNA Damage Repair Pathways

Protein poly ADP-ribosylation（PARylation） is a widespread post-translational modification at DNA lesions,which is catalyzed by poly（ADP-ribose） polymerases（PARPs）.This modification regulates a number of biological processes including chromatin reorganization,DNA damage response（DDR）,transcriptional regulation,apoptosis,and mitosis.PARP1,functioning as a DNA damage sensor,can be activated by DNA lesions,forming PAR chains that serve as a docking platform for DNA repair factors with high biochemical complexity.Here,we highlight molecular insights into PARylation recognition,the expanding role of PARylation in DDR pathways,and the functional interaction between PARylation and ubiquitination,which will offer us a better understanding of the biological roles of this unique post-translational modification.

ADP-ribosylhydrolases:from DNA damage repair to COVID-19

Adenosine diphosphate(ADP)-ribosylation is a unique post-translational modification that regulates many biological processes,such as DNA damage repair.During DNA repair,ADP-ribosylation needs to be reversed by ADP-ribosylhydrolases.A group of ADP-ribosylhydrolases have a catalytic domain,namely the macrodomain,which is conserved in evolution from prokaryotes to humans.Not all macrodomains remove ADP-ribosylation.One set of macrodomains loses enzymatic activity and only binds to ADP-ribose(ADPR).Here,we summarize the biological functions of these macrodomains in DNA damage repair and compare the structure of enzymatically active and inactive macrodomains.Moreover,small molecular inhibitors have been developed that target macrodomains to suppress DNA damage repair and tumor growth.Macrodomain proteins are also expressed in pathogens,such as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).However,these domains may not be directly involved in DNA damage repair in the hosts or pathogens.Instead,they play key roles in pathogen replication.Thus,by targeting macrodomains it may be possible to treat pathogen-induced diseases,such as coronavirus disease 2019(COVID-19).