J. Biol. Chem., Vol. 268, Issue 34, 25376-25384, Dec, 1993
Growth factor-inducible alternative splicing of nontransmembrane phosphotyrosine phosphatase PTP-1B pre-mRNA
VI Shifrin and BG Neel
Molecular Medicine Unit, Beth Israel Hospital, Boston, Massachusetts 02215.
PTP-1B is a major nontransmembrane phosphotyrosine phosphatase in human
cell lines and tissues, but its physiological function(s) and mechanism(s)
of regulation are largely unknown. We have found that in human diploid
fibroblasts a novel PTP-1B mRNA isoform is produced upon stimulation of
quiescent cells with a variety of growth factors. Generation of this
isoform requires protein synthesis, suggesting that the product(s) of an
immediate early response gene(s) is required. RNase protection and reverse
transcription polymerase chain reaction analysis demonstrate that the
isoform arises as a consequence of alternative pre-mRNA splicing, leading
to retention of the last intron. The novel isoform is found on
polyribosomes, indicating that it is actively translated, and is variably
expressed in human tissues. Sequence analysis indicates that the isoform
encodes a PTP-1B protein with an altered C terminus. To our knowledge, this
is the first example of growth factor-regulated alternative splicing.