FIG. 4.

Comparison of two cDNA sequences and deduced protein sequences cloned from 10W−1L cells. (A) The nucleotide sequence of cDNA encoding Gab1 was cloned by 5′- and 3′-RACE strategy. Although hamster Gab1 is composed of 694 amino acids (2,085 nucleotide bases for the coding region), only the amino-terminal sequence of 120 amino acids (up to ³⁶⁰A in the nucleotide sequence) is shown here. Two cDNAs were cloned from 10W−1L, one of which (the minor product) was identical with cDNA from nontransformed SHE 83-9. A cDNA product specific to 10W−1L lacks the upstream sequence to ⁷³G of the coding region of the original hamster Gab1 cDNA, and that sequence has been replaced by an uncharacterized sequence of at least 34 nucleotide bases, 5′-GAGATCTGCTGGGCTTCTCGGGGTTTGGTATCTT-3′ (sense), followed by the common sequence to the 3′ end. Therefore, translation of the product specific to 10W−1 starts from ³¹⁰ATG (M¹⁰⁴), instead of ¹ATG (M¹). A 5′ primer named −14F (5′-TCGCGGCGTGCACCATGAGCGGCGGCGAAG-3′; sense) is specific to cDNA encoding Gab1, while another 5′ primer named LSP (5′-GAGATCTGCTGGGCTTCTCGGGGTT-3′; sense) is specific to cDNA encoding Gab1^Δ1-103. Dashes, nucleotide bases of Gab1^Δ1-103 identical with those of hamster Gab1. (B) Comparison of the protein structures of Gab1 and Gab1^Δ1-103. Gab1^Δ1-103 lacks most of the amino-terminal PH domain (amino acids 14 to 116) observed in Gab1 and shares downstream structure including the MBD with Gab1.