title: The rat alpha1, 3-fucosyltransferase (rFucT-IV) gene encodes both long and short forms of the enzyme which share the same intracellular location.
abstract: Fucosyltransferase (FucT) activity has been detected on the surface of mouse germ cells and rat Sertoli cells, and has been postulated to play a role in cell-cell interactions. A recently cloned rat FucT (rFucT-IV) is expressed in the testes, and thus is a candidate for encoding the cell-surface FucT activity. This study maps the 5'-ends of several rFuc-T-IV mRNAs, and these results suggest that initiation of transcription may occur both upstream of the first ATG, as well as between the first two closely spaced, in-frame ATGs. Thus, in certain tissues, notably spleen, significant amounts of both a long and a short form of rFucT-IV would be predicted. This study also determines some basic properties of both the long and short forms of rFucT-IV, and investigates whether the use of alternative ATGs would allow FucT activity to be expressed both on the cell surface and in the Golgi. Plasmids that encode FLAG-epitope-labeled rFucT-IVs that initiate from either of the two ATGs were constructed, and rFucT-IV was expressed either in vitro using cell-free rabbit reticulocyte lysate, or after transfection in tissue culture. The results from these studies demonstrate that rFucT-IV is a glycosylated, transmembrane protein with a short cytoplasmic tail, and that either of the two ATGs in the 5' region of the rFucT-IV gene are capable of acting as functional initiators of translation in vitro, to produce enzymatically active glycoproteins. However, no difference in the intracellular localization between the transferase containing a 48 amino acid or a 15 amino acid cytoplasmic tail was detected by immunocytochemistry, as both show the same pattern of Golgi-like staining in several different cell types, with no indication of surface expression. Thus, the additional amino-terminal 33 amino acids of the long form of rFucT-IV do not appear to influence its intracellular location in the cell types investigated.
authors.affiliation: Biomedical Sciences Department, E.K. Shriver Center, Waltham, MA 02254, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Aucoin
authors.forename: O
authors.initials: O
authors.lastname: Koul
authors.forename: E M
authors.initials: EM
authors.lastname: Sajdel-Sulkowska
authors.forename: T
authors.initials: T
authors.lastname: Baboval
authors.forename: F I
authors.initials: FI
authors.lastname: Smith
mesh_terms: D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017931:DNA Primers; D005647:Fucosyltransferases / Q000235:genetics* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D011994:Recombinant Proteins; D005647:Fucosyltransferases; C031692:galactoside 3-fucosyltransferase