Generation of RNase L knockout cell lines by CRISPR/Cas system / 军事医学

Objective To establish RNase L gene knockout HEK 293 cell lines using CRISPR/Cas9 system.Methods Small guide RNA ( sgRNA) sequences of human RNase L were designed and sgRNAs were inserted into pCas-Guide and pCas-guide RNA(gRNA) vectors were obtained.The donor DNA sequences of the homologous arm were designed for RNase L knockout .In the presence of the right homologous arm , the resistance gene of hygromycin B and the left homologous arm as templates of homology-directed repair , the donor DNA template was amplified by overlopping PCR and cloned into the pBackZero-T expression vector and pBackZero-T-RNase LK vector was obtained .The pCas-gRNA vector and pBackZero-T-RNase LK vector were co-transfected into HEK293 cells to establish the stable expression cell line of RNase L gene knockout .Cells were cultured with hygromycin B , while Western blotting and DNA sequencing were used to analyze the gene of RNase L knockout from genome .Results and Conclusion The pCas-gRNA vector and pBackZero-T-RNase LK vector were successfully constructed.Five RNase L gene knockout HEK293 cell lines were generated,contributing to the study of the biological function and molecular mechanism of RNase L .

Expression, purification and characterization of the interferon-inducible, antiviral and tumour-suppressor protein, human RNase L.

The interferon (IFN)-inducible, 2′,5′-oligoadenylate (2-5A)-dependent ribonuclease L (RNase L) plays key role in antiviral defense of mammalian cells. Induction by IFN and activation by double-stranded RNA lead to 2-5A cofactor synthesis, which activates RNase L by causing its dimerization. Active RNase L degrades single-stranded viral as well as cellular RNAs causing apoptosis of virus-infected cells. Earlier, we had reported that expression of recombinant human RNase L caused RNA-degradation and cell-growth inhibition in E. coli without the need for exogenous 2-5A. Expression of human RNase L in E. coli usually leads to problems of leaky expression, low yield and degradation of the recombinant protein, which demands number of chromatographic steps for its subsequent purification thereby, compromising its biochemical activity. Here, we report a convenient protocol for expression of full-length, soluble and biochemically active recombinant human RNase L as GST-RNase L fusion protein from E. coli utilizing a single-step affinity purification with an appreciable yield of the highly purified protein. Recombinant RNase L was characterized by SDS-PAGE, immunoblotting and MALDI-TOF analysis. A semi-quantitative agarose-gel-based ribonuclease assay was developed for measuring its 2-5A-dependent RNase L activity against cellular large rRNAs as substrates. The optimized expression conditions minimized degradation of the protein, making it a convenient method for purification of RNase L, which can be utilized to study effects of various agents on the RNase L activity and its protein– protein interactions.