title: Bcl2 induces DNA replication stress by inhibiting ribonucleotide reductase.
abstract: DNA replication stress is an inefficient DNA synthesis process that leads replication forks to progress slowly or stall. Two main factors that cause replication stress are alterations in pools of deoxyribonucleotide (dNTP) precursors required for DNA synthesis and changes in the activity of proteins required for synthesis of dNTPs. Ribonucleotide reductase (RNR), containing regulatory hRRM1 and catalytic hRRM2 subunits, is the enzyme that catalyzes the conversion of ribonucleoside diphosphates (NDP) to deoxyribonucleoside diphosphates (dNDP) and thereby provides dNTP precursors needed for the synthesis of DNA. Here, we demonstrate that either endogenous or exogenous expression of Bcl2 results in decreases in RNR activity and intracellular dNTP, retardation of DNA replication fork progression, and increased rate of fork asymmetry leading to DNA replication stress. Bcl2 colocalizes with hRRM1 and hRRM2 in the cytoplasm and directly interacts via its BH4 domain with hRRM2 but not hRRM1. Removal of the BH4 domain of Bcl2 abrogates its inhibitory effects on RNR activity, dNTP pool level, and DNA replication. Intriguingly, Bcl2 directly inhibits RNR activity by disrupting the functional hRRM1/hRRM2 complex via its BH4 domain. Our findings argue that Bcl2 reduces intracellular dNTPs by inhibiting ribonucleotide reductase activity, thereby providing insight into how Bcl2 triggers DNA replication stress.
authors.affiliation: Authors' Affiliations: Departments of Radiation Oncology, Hematology and Medical Oncology, and Biochemistry, Emory University School of Medicine and Winship Cancer Institute of Emory University, Atlanta, Georgia; and Department of Clinical and Molecular Pharmacology, City of Hope National Medical Center, Duarte, California.
authors.forename: Maohua
authors.initials: M
authors.lastname: Xie
authors.forename: Yun
authors.initials: Y
authors.lastname: Yen
authors.forename: Taofeek K
authors.initials: TK
authors.lastname: Owonikoko
authors.forename: Suresh S
authors.initials: SS
authors.lastname: Ramalingam
authors.forename: Fadlo R
authors.initials: FR
authors.lastname: Khuri
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Curran
authors.forename: Paul W
authors.initials: PW
authors.lastname: Doetsch
authors.forename: Xingming
authors.initials: X
authors.lastname: Deng
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004249:DNA Damage; D004261:DNA Replication; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D025521:Tumor Suppressor Proteins; D012264:Ribonucleotide Reductases