title: Poldip2 knockout results in perinatal lethality, reduced cellular growth and increased autophagy of mouse embryonic fibroblasts.
abstract: Polymerase-δ interacting protein 2 (Poldip2) is an understudied protein, originally described as a binding partner of polymerase delta and proliferating cell nuclear antigen (PCNA). Numerous roles for Poldip2 have been proposed, including mitochondrial elongation, DNA replication/repair and ROS production via Nox4. In this study, we have identified a novel role for Poldip2 in regulating the cell cycle. We used a Poldip2 gene-trap mouse and found that homozygous animals die around the time of birth. Poldip2-/- embryos are significantly smaller than wild type or heterozygous embryos. We found that Poldip2-/- mouse embryonic fibroblasts (MEFs) exhibit reduced growth as measured by population doubling and growth curves. This effect is not due to apoptosis or senescence; however, Poldip2-/- MEFs have higher levels of the autophagy marker LC3b. Measurement of DNA content by flow cytometry revealed an increase in the percentage of Poldip2-/- cells in the G1 and G2/M phases of the cell cycle, accompanied by a decrease in the percentage of S-phase cells. Increases in p53 S20 and Sirt1 were observed in passage 2 Poldip2-/- MEFs. In passage 4/5 MEFs, Cdk1 and CyclinA2 are downregulated in Poldip2-/- cells, and these changes are reversed by transfection with SV40 large T-antigen, suggesting that Poldip2 may target the E2F pathway. In contrast, p21CIP1 is increased in passage 4/5 Poldip2-/- MEFs and its expression is unaffected by SV40 transfection. Overall, these results reveal that Poldip2 is an essential protein in development, and underline its importance in cell viability and proliferation. Because it affects the cell cycle, Poldip2 is a potential novel target for treating proliferative conditions such as cancer, atherosclerosis and restenosis.
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: David I
authors.initials: DI
authors.lastname: Brown
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Bernard
authors.initials: B
authors.lastname: Lassègue
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Minyoung
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Rostam
authors.initials: R
authors.lastname: Zafari
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: James S
authors.initials: JS
authors.lastname: Long
authors.affiliation: Department of Radiation Oncology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Harold I
authors.initials: HI
authors.lastname: Saavedra
authors.affiliation: Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Griendling
mesh_terms: D000818:Animals; D017209:Apoptosis; D001343:Autophagy; D002453:Cell Cycle; D049109:Cell Proliferation; D004260:DNA Repair; D004261:DNA Replication; D005260:Female; D005347:Fibroblasts / Q000166:cytology*; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D005838:Genotype; D006720:Homozygote; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; C514737:mitogenin 1 protein, mouse