title: Diadenosine 5', 5'''-P(1),P(4)-tetraphosphate (Ap4A) is synthesized in response to DNA damage and inhibits the initiation of DNA replication.
abstract: The level of intracellular diadenosine 5', 5'''-P(1),P(4)-tetraphosphate (Ap4A) increases several fold in mammalian cells treated with non-cytotoxic doses of interstrand DNA-crosslinking agents such as mitomycin C. It is also increased in cells lacking DNA repair proteins including XRCC1, PARP1, APTX and FANCG, while >50-fold increases (up to around 25 μM) are achieved in repair mutants exposed to mitomycin C. Part of this induced Ap4A is converted into novel derivatives, identified as mono- and di-ADP-ribosylated Ap4A. Gene knockout experiments suggest that DNA ligase III is primarily responsible for the synthesis of damage-induced Ap4A and that PARP1 and PARP2 can both catalyze its ADP-ribosylation. Degradative proteins such as aprataxin may also contribute to the increase. Using a cell-free replication system, Ap4A was found to cause a marked inhibition of the initiation of DNA replicons, while elongation was unaffected. Maximum inhibition of 70-80% was achieved with 20 μM Ap4A. Ap3A, Ap5A, Gp4G and ADP-ribosylated Ap4A were without effect. It is proposed that Ap4A acts as an important inducible ligand in the DNA damage response to prevent the replication of damaged DNA.
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Marriott
authors.affiliation: Division of Biomedical and Life Sciences, University of Lancaster, Lancaster LA1 4YG, UK.
authors.forename: Nikki A
authors.initials: NA
authors.lastname: Copeland
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
authors.forename: Ryan
authors.initials: R
authors.lastname: Cunningham
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Wilkinson
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK. Electronic address: agmclen@liv.ac.uk.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: McLennan
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Jones
mesh_terms: D016475:3T3 Cells; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D049109:Cell Proliferation / Q000187:drug effects; D002852:Chromatography, Ion Exchange; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004261:DNA Replication; D015226:Dinucleoside Phosphates / Q000096:biosynthesis* / Q000737:chemistry; D004852:Epoxy Compounds / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D016685:Mitomycin / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D015226:Dinucleoside Phosphates; D004852:Epoxy Compounds; D034741:RNA, Small Interfering; D000246:Adenosine Diphosphate Ribose; D016685:Mitomycin; C020733:diadenosine tetraphosphate; C007366:diepoxybutane; D011065:Poly(ADP-ribose) Polymerases; D010744:Phosphoric Monoester Hydrolases
keywords: ADP-ribosylation; Cell signaling; DNA damage; DNA replication; Diadenosine tetraphosphate