Fish Physiology and Biochemistry

, Volume 41, Issue 5, pp 1155–1171

c-myc in whitefish (Coregonus lavaretus): structure, expression, and insights into possible posttranscriptional regulatory mechanism

  • P. Brzuzan
  • C. Kramer
  • A. Łakomiak
  • E. Jakimiuk
  • M. Florczyk
  • M. Woźny
Article

DOI: 10.1007/s10695-015-0077-2

Cite this article as:
Brzuzan, P., Kramer, C., Łakomiak, A. et al. Fish Physiol Biochem (2015) 41: 1155. doi:10.1007/s10695-015-0077-2

Abstract

c-myc has a crucial function in growth control, differentiation, and apoptosis of vertebrate cells. Despite the important role of c-myc in mediating the biological effects, studies of c-myc gene expression and factors that control it in organisms other than mammals, such as fish, have been rare. In the current study, we asked whether c-myc mRNA of whitefish, a feasible organism for pollution monitoring in aquatic systems and a model in toxicological research, contains activity sites for regulatory motifs in its 5′- and 3′-UTRs, similar to those found in mammals. We were particularly interested in whether miRNA-34, a known negative regulator of c-myc’s in mammals, is able to regulate c-myc in fish. To answer these questions, we determined the mRNA sequence of whitefish c-myc and inferred the structure of the protein that it codes for. We found that the active sites of mRNA and structures of the inferred c-myc protein are similar to those found in mammals and other fish. Remarkably, levels of c-myc mRNA expression were very high in ovaries compared to other tissues of whitefish, thus corroborating previous data in fish. Using bioinformatic searches on c-myc 3′-UTR, we confirmed the presence of two miRNA-34a (miR-34a) response elements. Luciferase reporter assay showed that activity of reporters containing either the miR response elements or entire c-myc 3′-UTR was significantly reduced (p < 0.001) by ectopic expression of miR-34a. Therefore, we further investigated possible involvement of miR-34a in c-myc gene silencing by profiling the expression of both genes in livers of whitefish treated for 8, 24, 48 h with MC-LR, a potent c-myc inducer in mammals. Although the difference was only significant at p = 0.08, the expression of c-myc mRNA in challenged whitefish after 24 h of the treatment was notably higher than that in livers of control fish. Concurrently, we noticed slight but significant up-regulation of miR-34a after 24 and 48 h of the challenge (p < 0.05); however, we found no significant correlation of the c-myc mRNA levels and miR-34a expression. Together, these results suggest that miR-34a might regulate c-myc gene expression in whitefish liver; however, their involvement in MC-LR hepatotoxicity should be clarified in future studies.

Keywords

c-myc Microcystin-LR MicroRNA miR-34a Reporter analysis 

Supplementary material

10695_2015_77_MOESM1_ESM.doc (44 kb)
Supplementary material 1 (DOC 44 kb)
10695_2015_77_MOESM2_ESM.docx (19 kb)
Supplementary material 2 (DOCX 18 kb)
10695_2015_77_MOESM3_ESM.docx (14 kb)
Supplementary material 3 (DOCX 13 kb)
10695_2015_77_MOESM4_ESM.xlsx (26 kb)
Supplementary material 4 (XLSX 25 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • P. Brzuzan
    • 1
  • C. Kramer
    • 1
  • A. Łakomiak
    • 1
  • E. Jakimiuk
    • 2
  • M. Florczyk
    • 1
  • M. Woźny
    • 1
  1. 1.Department of Environmental Biotechnology, Faculty of Environmental SciencesUniversity of Warmia and Mazury in OlsztynOlsztynPoland
  2. 2.Department of Veterinary Prevention and Feed Hygiene, Faculty of Veterinary MedicineUniversity of Warmia and Mazury in OlsztynOlsztynPoland

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