The growth factor bound protein GrRB2, a 25-kDa cytosolic protein, plays a
key role in two separate pathways of the insulin signal transduction system
leading from the insulin receptor to the Ras proteins and thus affecting m
itogenic signaling. GRB2 regulates Ras activation through association with
the guanine nucleotide exchange factor Sos. The GRB2/Sos complex can connec
t with insulin receptor substrate 1 (IRS-1), which is one of the primary ta
rgets of the insulin and insulin-like growth factor receptors. In a second
pathway, independent of IRS-1, GRB2 links the insulin receptor to Ras signa
ling through another adapter protein, called Shc. In protooncogenic and oth
er noninsulin signaling systems, GRB2 appears to link receptor tyrosine kin
ases to Ras in similar pathways as well. This study presents the exon-intro
n organization of the human GRB2 gene. After primers were placed across the
known mRNA sequence, Long PCR products spanning introns and their adjacent
splice sites were amplified and adequately sequenced to establish the spli
ce sites and flanking regions. The gene was found to consist of five exons
(ranging from 78 to 186 bp) and of four introns (from similar to 1 to simil
ar to 7 kb). Intron primers for the respective exons were generated using t
he newly found flanking sequences. All exons were successfully amplified an
d sequenced, and the data obtained from Long PCR sequencing were confirmed.
(C) 1999 Academic Press.