Proteomics was used to identify a protein encoded by ORF 3a in a SARS-associated coronavirus (SARS-CoV). Immuno-blotting revealed that interchain disulfide bonds might be formed between this protein and the spike protein. ELISA indicated that sera from SARS patients have significant positive reactions with synthesized peptides derived from the 3a protein. These results are concordant with that of a spike protein-derived peptide. A tendency exists for co-mutation between the 3a protein and the spike protein of SARS-CoV isolates, suggesting that the function of the 3a protein correlates with the spike protein. Taken together, the 3a protein might be tightly correlated to the spike protein in the SARS-CoV functions. The 3a protein may serve as a new clinical marker or drug target for SARS treatment.

Diabetic wounds are recalcitrant to healing. However, the mechanism causing this dysfunction is not fully understood. High expression of matrix metalloproteinase-9 (MMP-9) is indicative of poor wound healing. In this study, we show that specificity protein-1 (Sp1), a regulator of MMP-9, binds directly to its promoter and enhances its expression. Additionally, we demonstrated that Sp1 is the direct target of two microRNAs (miRNAs), miR-129 and -335, which are significantly downregulated in diabetic skin tissues. In vitro experiments confirmed that miR-129 or -335 overexpression inhibits MMP-9 promoter activity and protein expression by targeting Sp1, whereas the inhibition of these miRNAs has the opposite effect. The beneficial role of miR-129 or miR-335 in diabetic wound healing was confirmed by the topical administration of miRNA agomirs in diabetic animals. This treatment downregulated Sp1-mediated MMP-9 expression, increased keratinocyte migration, and recovered skin thickness and collagen content. The combined treatment with miR-129 and miR-335 induced a synergistic effect on Sp1 repression and MMP-9 downregulation both in vitro and in vivo. This study demonstrates the regulatory mechanism of Sp1-mediated MMP-9 expression in diabetic wound healing and highlights the potential therapeutic benefits of miR-129 and -335 in delayed wound healing in diabetes.

Spike protein is one of the major structural proteins of severe acute respiratory syndrome-coronavirus. It is essential for the interaction of the virons with host cell receptors and subsequent fusion of the viral envelop with host cell membrane to allow infection. Some spike proteins of coronavirus, such as MHV, HCoV-OC43, AIBV and BcoV, are proteolytically cleaved into two subunits, S1 and S2. In contrast, TGV, FIPV and HCoV-229E are not. Many studies have shown that the cleavage of spike protein seriously affects its function. In order to investigate the maturation and proteolytic processing of the S protein of SARS CoV, we generated S1 and S2 subunit specific antibodies (Abs) as well as N, E and 3CL protein-specific Abs. Our results showed that the antibodies could efficiently and specifically bind to their corresponding proteins from E.coli expressed or lysate of SARS-CoV infected Vero-E6 cells by Western blot analysis. Furthermore, the anti-S1 and S2 Abs were proved to be capable of binding to SARS CoV under electron microscope observation. When S2 Ab was used to perform immune precipitation with lysate of SARS-CoV infected cells, a cleaved S2 fragment was detected with S2-specific mAb by Western blot analysis. The data demonstrated that the cleavage of S protein was observed in the lysate, indicating that proteolytic processing of S protein is present in host cells.