FIG. 3.
Tyrosines 325 and 343 are required for the association between Dok-3 and SHIP-1 in B cells. Pools of three independent transfectants of the indicated A20 derivatives were stimulated for various periods of time with F(ab′)2 fragments of SAM IgG. Following lysis, Dok-3 was immunoprecipitated from equivalent quantities of total cell proteins and probed by immunoblotting with anti-phosphotyrosine (Anti-P.tyr; top blocks) or anti-SHIP-1 (middle blocks). The presence of Dok-3 was confirmed by immunoblotting of equivalent amounts of total cell lysates with anti-Dok-3 (bottom blocks). (A) Comparison of Dok-3 FFYY and Dok-3 YYFF. Note that a small amount of Dok-3-associated SHIP-1 could be seen upon longer autoradiographic exposures in cells expressing the neo gene or Dok-3 FFYY (data not shown). This is presumably due to an interaction between endogenous Dok-3 and SHIP-1. (B) Comparison of Dok-3 Y325F and Dok-3 Y343F.