Molecular cloning of cDNA encoding a ubiquitin-activating enzyme (E1) from goldfish (Carassius auratus) and expression analysis of the cloned gene

The core ubiquitin system of mandarin fish, Siniperca chuatsi, can be utilized by infectious spleen and kidney necrosis virus

The process of ubiquitination regulates various cellular processes. The ubiquitin-proteasome system (UPS) in fish, which is important for the generation of innate and adaptive immune responses to pathogens, is the target of aquatic viruses to achieve immune evasion. We cloned and characterized three genes, namely, a ubiquitin-activating enzyme (ScE1), a ubiquitin-conjugating enzyme (ScE2), and a HECT-type ubiquitin ligase (ScE3) of mandarin fish Siniperca chuatsi. The genes were expressed in all tissues and the highest levels were observed in the blood. In infectious spleen and kidney necrosis virus (ISKNV)-infected mandarin fish fry cells, the expression levels of the three genes in vitro were almost identical, and upregulated during the early stage and downregulated at the late stage. In the blood of ISKNV-infected mandarin fish, their expressions in vivo were downregulated equally although peaking at different timepoints, indicating the suppression of UPS by viral infection. Furthermore, these recombinant proteins were determined to function well in ubiquitination assays in vitro. Moreover, ScE1 and ScE2 can be utilized by four RING-type viral E3s (vE3s) that are encoded by ISKNV. The in vitro activity of vE3 was stronger than that of ScE3, suggesting that the fish UPS may be hijacked by ISKNV via E3 activity competition and expression modulation. The present study investigated the function of mandarin fish UPS as well as its response to iridovirus infection, providing insights to better understand the virus-host interactions and the mechanism of ISKNV in evading host immune responses.

Molecular Cloning of cDNA Encoding APC11, a Catalytic Component of Anaphase-promoting-complex (APC/C), from Goldfish (Carassius auratus), and Establishment ofin vitroUbiquitinating System

Destruction of cyclin B is required for exit from mitosis and meiosis. A cyclin-degrading system, including anaphase-promoting-complex/cyclosome (APC/C), has been shown to be responsible for cyclin B destruction. Here we present the cloning, sequencing, and expression analysis of goldfish (Carassius auratus) APC11, which encodes the catalytic component of APC/C from goldfish ovary. The cloned cDNA is 348 bp long and encodes 88 amino acids. The deduced amino acid sequence is highly homologous to APC11 from other species. The expression of mRNA for APC11 was ubiquitous among tissues, as opposed to that of mRNA for E2-C, which occurred at a very high level in the ovary. Recombinant goldfish APC11 possesses ubiquitinating activity against cyclin B. We established an in vitro ubiquitinating system of proteins composed of purified recombinant E1, E2-C, and APC11 from goldfish. The reconstructed system for these ubiquitinating enzymes makes it feasible to elucidate the molecular mechanism of cyclin B degradation.

Molecular cloning of cDNA encoding polypeptide chain elongation factor 1alpha from goldfish (Carassius auratus)

The goldfish homologue of polypeptide chain elongation factor-1alpha (EF-1alpha) isolated from the ovary of the goldfish is described. The deduced amino acid sequence is highly homologous to EF-1alpha from other species. Analysis of its tissue distribution revealed a single 1.7 kilobase message ubiquitous among various tissues.