Cloning and expression of hnRNP A2 gene,purification as well as clinical application of the recombinant protein
Objective To clone and express the heterogeneous nuclear ribonucleoprotein (hnRNP) A2 gene and to detect anti-hnRNP A2/RA33 antibody with the purified recombinant protein. Methods Total RNA was isolated from peripheral blood mononuclear cells (PBMC) and the RT-PCR was performed. The fragment was cloned into pUC-T1 plasmids and sequenced. The expression vector, pET28a-hnRNP A2 was constructed and transformed into E.coli BL21(DE3)plys S for inducing expression. Metal chelate resin chromatography colum was used to purify hnRNP A2 with high purity and activity. The serum of 97 patients with RA, 50 patients with SLE, 8 patients with MCTD, 99 patients with other diffused rheumatic diseases, 29 patients with other arthritis and 40 controls were examined by ELISA with the purified recombinant hnRNP A2 antigen. Results The expression vector pET28a-hnRNP A2 was constructed with high-level expression. The sensitivity of anti-hnRNP A2/RA33 in RA, SLE, MCTD, other arthritis and other CTD was shown as 36.8%, 24%, 75%, 3.57% and 10.10% respectively. The specificity of anti-hnRNP A2/RA33 in RA was 86.67%. Conclusion Detection of anti-hnRNP A2/RA33 antibody with genetic recombinant hnRNP A2 antigen is a reliable method for early diagnosis of RA.