The gene structure of the human growth factor bound protein GRB2.

The growth factor bound protein GRB2, 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 mitogenic signaling. GRB2 regulates Ras activation through association with the guanine nucleotide exchange factor Sos. The GRB2/Sos complex can connect with insulin receptor substrate 1 (IRS-1), which is one of the primary targets of the insulin and insulin-like growth factor receptors. In a second pathway, independent of IRS-1, GRB2 links the insulin receptor to Ras signaling through another adapter protein, called Shc. In protooncogenic and other noninsulin signaling systems, GRB2 appears to link receptor tyrosine kinases to Ras in similar pathways as well. This study presents the exon-intron 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 splice sites and flanking regions. The gene was found to consist of five exons (ranging from 78 to 186 bp) and of four introns (from approximately 1 to approximately 7 kb). Intron primers for the respective exons were generated using the newly found flanking sequences. All exons were successfully amplified and sequenced, and the data obtained from Long PCR sequencing were confirmed.