Phosphate depletion enhances the stability of the amphotropic murine leukemia virus receptor mRNA

Through its specific receptor, the amphotropic murine leukemia virus (MLV) infects cells from many mammals, including humans. We have previously demonstrated that levels of human amphotropic MLV receptor (pit2) mRNA varied considerably in different human cell lines. Removal of phosphate from the culture medium led to increases in the amount of pit2 mRNA and the quantity of a 71-kDa protein specifically recognized by antibodies against Pit2. To determine if the increases in pit2 mRNA and protein levels were due to a transcriptional effect, the pit2 promoter region was cloned. This region was characterized and found to contain a functional TATA-less promoter that under our experimental conditions does not respond to phosphate depletion. Instead, pit2 mRNA was found to be more stable in response to Pi depletion. These results suggest that the increase in pit2 mRNA levels observed in response to Pi depletion occurs at a posttranscriptional level and is due to enhanced mRNA stability.