Two active and differently N-glycosylated isoforms of human ST3Gal-V are produced from the placental mRNA variant by a leaky scanning mechanism

Zava, Stefania; Milani, Simona; Sottocornola, Elena; Berra, Bruno; Colombo, Irma

doi:10.1016/j.febslet.2010.02.062

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Volume 584, Issue 8 , Pages 1476-1480, 16 April 2010

Two active and differently N-glycosylated isoforms of human ST3Gal-V are produced from the placental mRNA variant by a leaky scanning mechanism

Edited by Sandro Sonnino

Università degli Studi di Milano, Dipartimento di Scienze Molecolari Applicate ai Biosistemi, via Trentacoste 2, 20134 Milan, Italy

Received 28 December 2009; received in revised form 23 February 2010; accepted 23 February 2010. published online 26 February 2010.

Abstract

Previously, we identified a human ST3Gal-V mRNA variant peculiarly characterized by the presence of a translational start codon localized up-stream and in-frame with the one that is usually considered as unique translation initiation site in the human gene. In this study we demonstrate, by cDNA transfection experiments, mutational analyses, enzyme activity assays, and endoglycosidase-H treatments, that the in vivo expression of this transcript gives rise to two human ST3Gal-V isoforms with distinct characteristics. Produced by a leaky scanning mechanism, they carry different N-glycan structures and exhibit differences in their GM₃ synthase activity that might be relevant for the modulation of GM₃ cellular content.

Keywords: hST3Gal-V, GM₃, Translation start codon, N-Glycosylation