title: Nucleoside salvage pathway kinases regulate hematopoiesis by linking nucleotide metabolism with replication stress.
abstract: Nucleotide deficiency causes replication stress (RS) and DNA damage in dividing cells. How nucleotide metabolism is regulated in vivo to prevent these deleterious effects remains unknown. In this study, we investigate a functional link between nucleotide deficiency, RS, and the nucleoside salvage pathway (NSP) enzymes deoxycytidine kinase (dCK) and thymidine kinase (TK1). We show that inactivation of dCK in mice depletes deoxycytidine triphosphate (dCTP) pools and induces RS, early S-phase arrest, and DNA damage in erythroid, B lymphoid, and T lymphoid lineages. TK1(-/-) erythroid and B lymphoid lineages also experience nucleotide deficiency but, unlike their dCK(-/-) counterparts, they still sustain DNA replication. Intriguingly, dCTP pool depletion, RS, and hematopoietic defects induced by dCK inactivation are almost completely reversed in a newly generated dCK/TK1 double-knockout (DKO) mouse model. Using NSP-deficient DKO hematopoietic cells, we identify a previously unrecognized biological activity of endogenous thymidine as a strong inducer of RS in vivo through TK1-mediated dCTP pool depletion. We propose a model that explains how TK1 and dCK "tune" dCTP pools to both trigger and resolve RS in vivo. This new model may be exploited therapeutically to induce synthetic sickness/lethality in hematological malignancies, and possibly in other cancers.
authors.affiliation: Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA, USA.
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Austin
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Armijo
authors.forename: Dean O
authors.initials: DO
authors.lastname: Campbell
authors.forename: Arun S
authors.initials: AS
authors.lastname: Singh
authors.forename: Terry
authors.initials: T
authors.lastname: Hsieh
authors.forename: David
authors.initials: D
authors.lastname: Nathanson
authors.forename: Harvey R
authors.initials: HR
authors.lastname: Herschman
authors.forename: Michael E
authors.initials: ME
authors.lastname: Phelps
authors.forename: Owen N
authors.initials: ON
authors.lastname: Witte
authors.forename: Johannes
authors.initials: J
authors.lastname: Czernin
authors.forename: Caius G
authors.initials: CG
authors.lastname: Radu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001973:Bromodeoxyuridine; D004261:DNA Replication / Q000502:physiology*; D003842:Deoxycytidine Kinase / Q000235:genetics / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000378:metabolism; D005434:Flow Cytometry; D006410:Hematopoiesis / Q000502:physiology*; D016130:Immunophenotyping; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009705:Nucleosides / Q000378:metabolism*; D009711:Nucleotides / Q000172:deficiency* / Q000378:metabolism; D013312:Stress, Physiological / Q000502:physiology*; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism
chemical_list: D003845:Deoxycytosine Nucleotides; D009705:Nucleosides; D009711:Nucleotides; C024107:2'-deoxycytidine 5'-triphosphate; D013937:Thymidine Kinase; D003842:Deoxycytidine Kinase; D001973:Bromodeoxyuridine