Structure and Expression of the Gene Encoding Secretor‐Type Galactoside 2‐α‐l‐fucosyltransferase (FUT2)

The expression and secretion of ABO antigens in epithelial cells of glands are controlled by secretor‐type α(1,2) fucosyltransferase activity. We have examined the expression of the secretor‐type α(1,2)fucosyltransferase gene ( FUT2 ) and a pseudogene of FUT2 ( Sec1 ) in several tumor cell lines by northern blot and/or reverse‐transcription‐PCR (RT‐PCR) analyses. Transcripts of FUT2 were found in total RNA from ovarian, gastric and colonic cancer cell lines but not from six leukemic cell lines, including erythroleukemic HEL cells, by RT‐PCR. On the other hand, RT‐PCR indicated that Sec1 was expressed in all these tumor cells, including all hematopoietic cells studied. Northern blot analysis indicated that FUT2 transcripts with a similar size (3.3 kb) were expressed in cancer cell lines. Rapid amplification of cDNA ends suggested that the entire FUT2 cDNA is 3.1‐kb long and has two Alu repetitive elements in its 3′ untranslated region, including an inverted repeat. The mRNA, therefore, may form a large stem‐and‐loop structure (1.2 kb). Each stem contains about 300 bases, the loop contains 640 bases, and the percentage of complementary nucleotide sequences in the stem region is 85%. The presence of a large stem‐and‐loop structure in the 3′ untranslated region may regulate the level of the FUT2 transcript by effecting the stability of the mRNA.