In vitro analysis of a hammerhead ribozyme targeted to infectious bronchitis virus nucleocapsid mRNA

Current concepts in the development of therapeutics against human and animal coronavirus diseases by targeting NP

The coronavirus (CoV) infects a broad range of hosts including humans as well as a variety of animals. It has gained overwhelming concerns since the emergence of deadly human coronaviruses (HCoVs), severe acute respiratory syndrome coronavirus (SARS-CoV) in 2003, followed by Middle East respiratory syndrome coronavirus (MERS-CoV) in 2015. Very recently, special attention has been paid to the novel coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 due to its high mobility and mortality. As the COVID-19 pandemic continues, despite vast research efforts, the effective pharmaceutical interventions are still not available for clinical uses. Both expanded knowledge on structure insights and the essential function of viral nucleocapsid (N) protein are key basis for the development of novel, and potentially, a broad-spectrum inhibitor against coronavirus diseases. This review aimed to delineate the current research from the perspective of biochemical and structural study in cell-based assays as well as virtual screen approaches to identify N protein antagonists targeting not only HCoVs but also animal CoVs.

Inhibitory effect of maxizyme on mutant-type p53 in hepatocellular carcinoma

AIM: To investigate the inhibitory effect of maxizyme on the mutant-type p53 (mtp53) gene at codon 249 in exon 7 (AGG→AGT) in cell-free system, hepatocellular carcinoma (HCC) cell line MHCC97, and nude mice bearing human HCC, and to explore a new method for gene therapy of HCC.

METHODS: Anti-mtp53 and control mutant maxizyme were designed and then cloned into the vector pBSKU6 and pEGFPC1, respectively. The ³²p-labeled mtp53 transcript was the target mRNA. Cold maxizyme transcript was incubated with ³²p-labeled target RNA in cell-free system. The products were quantified by measuring the radioautographed count per minute (cpm) in 1 mL solution. The MHCC97 cells were the target cells which contained a mutation at the third-base position of codon 249 of the p53 gene(AGG→AGT). PEGFPMz (recombinant eukaryotic vector) was transfected into MHCC97 cells by LipofectamineTM2000. The expression of mtp53 was analyzed by Northern Blot and Western Blot. The nude mice bearing human liver cancer were prepared and divided into blank control pEGFP and pEGFPMz group. The growth curve of the tumor in mice and the survival rate of mice were observed. The expression of mtp53 mRNA were detected by reverse transcription polymerase chain reaction (PT-PCR).

RESULTS: The established pEGFPMz had the correct structure. Maxizyme had a specific cleavage activity for mtp53 with a cleavage efficiency of 49% extracellularly, while the wild type p53 was not cleaved. The control maxizyme had no significant effect on both mutant and wile type p53. After pEGFPMz were transfected into MHCC97 cells, the expression of mtp53 mRNA and protein in pEGFPMz group were 65% and 67% respectively, which were significantly lower than those in blank control and pEGFP group (P<0.05). The tumor size decreased and mtp53 mRNA was down-regulated in mice treated with pEGFPMz as compared with those in mice of blank control and pEGFP group (mtp53 mRNA: 0.95±0.13 vs 1.44±0.14, 1.47±0.12; P<0.05), and also the survivals of the mice in pEGFPMz were improved.

CONCLUSION: Maxizyme can effectively inhibit the expression of mtp53 mRNA and protein as well as the growth of hepatocellular carcinoma cells.