ABSTRACT
Thiamin pyrophosphate (TPP) is a thiamine (vitamin B1) derivative and an essential cofactor in oxidative metabolism of the sugars,fatty acids and amino acids in living cells.By now,numerous TPP-dependent artificial riboswitch systems have been developed to regulate target gene expression but limited in bacteria,fungi or plant cells.Herein,the activating (switch-on) and inhibiting (switch-off) TPP-depended hammerhead ribozyme switches,which are from previous reported structures of prokaryotes screening,were investigated in mammalian cells.These ribozyme switches were inserted into the 3'UTR of the enhanced green fluorescence protein (EGFP) gene to construct the efficient ribozyme-based artificial switches through overlap extension PCR cloning.The HEK293 cells were transfected with the engineered ribozyme switches at increasing concentration of TPP.The EGFP gene-regulatory ability was analyzed with fluorescent microscope and flow cytometry.These TPP-inducible gene regulation devices showed the obvious ligand dose-dependency and excellent specificity.Two switch-on and one switch-off constructs demonstrated 3.1-fold or 1.9-fold increment and 2.3-fold reduction of EGFP level respectively with 150 μ mol/L TPP.The ligand-responsive ribozyme switches,by tuning the change of TPP concentration into the visual reporter genetic expression in cells,enable an efficient development of label-free,noninvasive and high-specific biosensors in living mammalian cells.