title: Human DNA Ligase I Interacts with and Is Targeted for Degradation by the DCAF7 Specificity Factor of the Cul4-DDB1 Ubiquitin Ligase Complex.
abstract: The synthesis, processing, and joining of Okazaki fragments during DNA replication is complex, requiring the sequential action of a large number of proteins. Proliferating cell nuclear antigen, a DNA sliding clamp, interacts with and coordinates the activity of several DNA replication proteins, including the enzymes flap endonuclease 1 (FEN-1) and DNA ligase I that complete the processing and joining of Okazaki fragments, respectively. Although it is evident that maintaining the appropriate relative stoichiometry of FEN-1 and DNA ligase I, which compete for binding to proliferating cell nuclear antigen, is critical to prevent genomic instability, little is known about how the steady state levels of DNA replication proteins are regulated, in particular the proteolytic mechanisms involved in their turnover. Because DNA ligase I has been reported to be ubiquitylated, we used a proteomic approach to map ubiquitylation sites and screen for DNA ligase I-associated E3 ubiquitin ligases. We identified three ubiquitylated lysine residues and showed that DNA ligase I interacts with and is targeted for ubiquitylation by DCAF7, a specificity factor for the Cul4-DDB1 complex. Notably, knockdown of DCAF7 reduced the degradation of DNA ligase I in response to inhibition of proliferation and replacement of ubiquitylated lysine residues reduced the in vitro ubiquitylation of DNA ligase I by Cul4-DDB1 and DCAF7. In contrast, a different E3 ubiquitin ligase regulates FEN-1 turnover. Thus, although the expression of many of the genes encoding DNA replication proteins is coordinately regulated, our studies reveal that different mechanisms are involved in the turnover of these proteins.
authors: From the Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131 and.
authors: Zhimin
authors: Z
authors: Peng
authors: the Department of Anatomy and Neurobiology and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors: Zhongping
authors: Z
authors: Liao
authors: From the Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131 and.
authors: Yoshihiro
authors: Y
authors: Matsumoto
authors: the Department of Anatomy and Neurobiology and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201.
authors: Austin
authors: A
authors: Yang
authors: From the Departments of Internal Medicine and Molecular Genetics and Microbiology, and the University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131 and atomkinson@salud.unm.edu.
authors: Alan E
authors: AE
authors: Tomkinson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D000072481:DNA Ligase ATP / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D045585:Flap Endonucleases / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis; D054875:Ubiquitination / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D044842:Cullin Proteins; C515143:DCAF7 protein, human; C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D009097:Multienzyme Complexes; D045585:Flap Endonucleases; C468317:FEN1 protein, human; D000072481:DNA Ligase ATP
keywords: DNA ligase I; DNA replication; cell cycle; proliferating cell nuclear antigen (PCNA); proteasome; protein turnover; proteolysis; ubiquitin; ubiquitin ligase; ubiquitylation