Gene transfer of truncated NGF receptor clones leads to cell surface expression in mouse fibroblasts

Transfection of recombinant bacteriophage clones encoding human NGF receptor sequences resulted in cell surface expression in mouse fibroblasts. Unexpectedly, receptors were expressed even after transfection with phage clones which lack 5' gene sequences. Stable transformants were purified and analyzed in detail. S1 nuclease protection and primer extension analysis revealed that an initiation site lies within an intron sequence in the middle of the receptor gene. A truncated mRNA transcript was detected that allowed for the expression of NGF receptors capable of binding to NGF. Since the original phage clones lacked the first two exons, these results suggest that the normal N-terminal sequences may not be necessary for cell surface expression and binding to NGF.