title: Molecular cloning, functional characterization and phylogenetic analysis of B-cell activating factor in zebrafish (Danio rerio).
abstract: B-cell activating factor (BAFF), belonging to the TNF family, is a critical cytokine for B-cell survival, proliferation, maturation and differentiation. In the present study we cloned the cDNA of zebrafish (Danio rerio) BAFF (designated zBAFF) by reverse transcription-PCR (RT-PCR). The open reading frame (ORF) of zBAFF consists of 807 bases encoding a protein of 268 amino acids. The deduced amino acid sequence of its cDNA possessed the TNF family signature, a transmembrane domain, and three cysteine residues, which are the typical characteristics of TNF gene in mammals and birds. Phylogenetic analysis exhibits the highest identity score 67.6, 61.4 and 66.9% with the rainbow trout, tetraodon and salmon counterparts, respectively. The identity to avian and mammalian BAFFs ranges from 49.7 to 53.8%. Recombinant soluble zBAFF (zsBAFF) was fused with a small ubiquitin-related modifier gene (SUMO) to enhance the soluble expression level in Escherichia coli BL21 (DE3). The resulting fused protein SUMO-zsBAFF was highly expressed in BL21 (DE3) with a molecular weight of 38 kDa. The fusing protein was purified using metal chellate affinity chromatography (Ni-NTA) and cleaved by a SUMO-specific protease, then confirmed by SDS-PAGE and Western blotting analysis. In vitro, the MTT assay indicated that the purified zsBAFF as well as SUMO-zsBAFF proteins were able to promote spleen lymphocyte survival in a dose-dependent manner also to co-stimulate the proliferation of mammalian B-cells with anti-IgM. Thus, the fusion protein represents a readily obtainable source of biologically active zsBAFF that may prove useful in further studies on zebrafish BAFF and its receptors.
authors.affiliation: Jiangsu Province Key Laboratory for Molecular and Medical Biotechnology, Life Sciences College, Nanjing Normal University, Nanjing 210046, China.
authors.forename: Zhenning
authors.initials: Z
authors.lastname: Liang
authors.forename: Yi
authors.initials: Y
authors.lastname: Kong
authors.forename: Caihong
authors.initials: C
authors.lastname: Luo
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Shuangquan
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D053264:B-Cell Activating Factor / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000276:immunology; D025842:SUMO-1 Protein / Q000276:immunology; D016415:Sequence Alignment; D015027:Zebrafish / Q000145:classification* / Q000235:genetics / Q000276:immunology / Q000502:physiology*
chemical_list: D053264:B-Cell Activating Factor; D011994:Recombinant Proteins; D025842:SUMO-1 Protein