title: Transgene-mediated co-suppression of DNA topoisomerase-1 gene in Caenorhabditis elegans.
abstract: Ectopic expression of multi-transgenic copies can result in reduced expression of the transgene and can induce silence of endogenous gene; this process is called as co-suppression. Using a transgene-mediated co-suppression technique, we demonstrated the biological function of DNA topoisomerase-1 (top-1) in C. elegans development. Introduction of full-length top-1 transgene sufficiently induced the co-suppression of endogenous top-1 gene, causing embryonic lethality and abnormal germline development. We also found that the co-suppression of top-1 gene affected morphogenesis, lifespan and larval growth that were not observed in top-1 (RNAi) animals. Strikingly, co-suppression effects were significantly reduced by the elimination of top-1 introns, suggesting that efficient co-suppression may require intron(s) in C. elegans. Sequence analysis revealed that the introns 1 and 2 of top-1 gene possess consensus binding sites for several transcription factors, including MAB-3, LIN-14, TTX-3/CEH-10, CEH-1, and CEH-22. Among them, we examined a genetic link between ceh-22 and top-1. The ceh-22 is partially required for the specification of distal tip cells (DTC), which functions as a stem cell niche in the C. elegans gonad. Intriguingly, top-1 (RNAi) significantly enhanced DTC loss in ceh-22 mutant gonads, indicating that top-1 may play an important role in CEH-22-mediated DTC fate specification. Therefore, our findings suggest that transgene-mediated co-suppression facilitates the silencing of the specific genes and the study of gene function in vivo.
authors: Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC 27834, USA ; Leo W. Jenkins Cancer Center, Brody School of Medicine, East Carolina University Greenville, NC 27834, USA ; Lineberger Comprehensive Cancer Center, University of North Carolina Chapel Hill, NC 27599, USA.
authors: Myon-Hee
authors: MH
authors: Lee
authors: Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC 27834, USA ; Department of Oriental Pharmacy, College of Pharmacy, Woosuk University Jeonbuk 565-701, Republic of Korea.
authors: Dong Seok
authors: DS
authors: Cha
authors: Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC 27834, USA.
authors: Srivalli Swathi
authors: SS
authors: Mamillapalli
authors: Department of Oncology, Brody School of Medicine, East Carolina University Greenville, NC 27834, USA.
authors: Young Chul
authors: YC
authors: Kwon
authors: Department of Biochemistry, Yonsei University Seoul 120-749, Republic of Korea.
authors: Hyeon-Sook
authors: HS
authors: Koo
keywords: Caenorhabditis elegans; DNA topoisomerase I; co-suppression; distal tip cells (DTCs); lifespan; morphogenesis