Regulation of CTP Synthase Filament Formation During DNA Endoreplication in Drosophila.
CTP synthase (CTPsyn) plays an essential role in DNA, RNA, and lipid synthesis. Recent studies in bacteria, yeast, and Drosophila all reveal a polymeric CTPsyn structure, which dynamically regulates its enzymatic activity. However, the molecular mechanism underlying the formation of CTPsyn polymers is not completely understood. In this study, we found that reversible ubiquitination regulates the dynamic assembly of the filamentous structures of Drosophila CTPsyn. We further determined that the proto-oncogene Cbl, an E3 ubiquitin ligase, controls CTPsyn filament formation in endocycles. While the E3 ligase activity of Cbl is required for CTPsyn filament formation, Cbl does not affect the protein levels of CTPsyn. It remains unclear whether the regulation of CTPsyn filaments by Cbl is through direct ubiquitination of CTPsyn. In the absence of Cbl or with knockdown of CTPsyn, the progression of the endocycle-associated S phase was impaired. Furthermore, overexpression of wild-type, but not enzymatically inactive CTPsyn, rescued the endocycle defect in Cbl mutant cells. Together, these results suggest that Cbl influences the nucleotide pool balance and controls CTPsyn filament formation in endocycles. This study links Cbl-mediated ubiquitination to the polymerization of a metabolic enzyme and reveals a role for Cbl in endocycles during Drosophila development.
Department of Biochemistry, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan Molecular Medicine Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Pei-Yu
PY
Wang
Molecular Medicine Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Wei-Cheng
WC
Lin
Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Yi-Cheng
YC
Tsai
Department of Biomedical Sciences, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan Healthy Aging Research Center, Chang Gung University.
Mei-Ling
ML
Cheng
Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Yu-Hung
YH
Lin
Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Shu-Heng
SH
Tseng
Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan.
Archan
A
Chakraborty
Department of Biochemistry, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan Molecular Medicine Research Center, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Kwei-Shan, Tao-Yuan, 333 Taiwan Chang Gung Memorial Hospital, Kwei-Shan, Tao-Yuan, 333 Taiwan pai@mail.cgu.edu.tw.
Li-Mei
http://orcid.org/0000-0002-1417-6432
LM
Pai
D000818:Animals; D019731:Carbon-Nitrogen Ligases / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism*; D004247:DNA; D004261:DNA Replication; D004330:Drosophila / Q000201:enzymology / Q000235:genetics*; D005260:Female; D054875:Ubiquitination
D004247:DNA; D019731:Carbon-Nitrogen Ligases; C019951:CTP synthetase
CTP synthase; Cbl; Drosophila; cytoophidia; endocycle