ALPHA-1,3-L-FUCOSYL-TRANSFERASE EXPRESSION IN DEVELOPING HUMAN MYELOID CELLS ANTIGENIC, ENZYMATIC, AND MESSENGER-RNA ANALYSES

In an attempt to correlate the cell surface expression of Le(x) and si alyl-Le(x) structures in immature and mature myeloid cells with the ge nes expressing alpha 1,3-fucosyltransferase(s) we have examined: 1) th e properties of the cellular alpha 1,3-fucosyltransferases and the mRN A transcripts corresponding to the five cloned genes, Fuc-TIII, Fuc-TI V, Fuc-TV, Fuc-TVI, and Fuc-TVII, in mature granulocytes and in the my eloid cell line HL-60, before and after dimethyl sulfoxide-induced dif ferentiation and 2) the properties of the alpha 1,3-fucosyltransferase s expressed in COS 7 cells transfected with plasmids containing Fuc-TI V and Fuc-TVII cDNAs. The previously shown increase in cell surface ex pression of sialyl-Le(x) on differentiation of HL-60 cells (Skacel P. O., Edwards A. J., Harrison C. T., and Watkins W. M. (1991) Blood 78, 1452-1460) is accompanied by a sharp fall in expression of Fuc-TIV mRN A and a persistence of expression of Fuc-TVII mRNA. The properties of the alpha 1,3-fucosyltransferase expressed in COS-7 cells transfected with Fuc-TIV are consistent with this being the major gene responsible for the expression of Le(x) in the immature myeloid cells. In Norther n blot analyses, no transcripts of Fuc-TIII, Fuc-TV, or Fuc-TVI were d etected in total RNA from mature granulocytes or mRNA from HL-60 cells before or after differentiation. In total RNA from mature granulocyte s, Fuc-TIV transcripts were only faintly visible, whereas Fuc-TVII tra nscripts were quite definitely expressed. The specificity properties o f Fuc-TVII expressed in COS-7 cells are consistent with this gene bein g the major candidate alpha 1,3-fucosyltransferase controlling the exp ression of sialyl-Le(x) on mature cells. However, Le(x) continues to b e expressed on the surface of mature granulocytes and cell extracts re tain the capacity to transfer fucose to non-sialylated acceptor substr ates. The question therefore remains as to whether these properties re sult from the weakly expressed Fuc-TIV gene or whether another alpha 1 ,3-fucosyltransferase gene remains to be identified.