• POGLUT1 is an ER resident, soluble, protein with O-Glucosyltransferase activity. It adds β-linked Glc to hydroxyl gp. of Ser specifically in EGF repeats.
• Rumi is the gene encoding for POGLUT1 activity. Rumi is essential for Notch signaling, and Rumi dysregulation is linked to several human diseases.
• The consensus sequence for this enzyme activity in EGF is C1-X-S-X-P/A-C2, where C1 and C2 are the first and second conserved Cys of the EGF repeat. Such a motif is predicted to occur in 40 proteins in mammals are 40 mammalian proteins.
• While initially identified in Factor VII and IX, it is heavily glycosylated on Notch. This is thus a penetrating gene that is E9.5 lethal in mice.
• O-glucose is typically extended by two α3-linked xyloses to the trisaccharide, Xyl(α1-3)Xyl(α1-3)Glcβ1-O-Ser in mammals, although mono- and di-saccharide forms have also been seen. Here, glucoside xylosyltransferases 1 and 2 (GXYLT1 and GXYLT2) adds the first α3-linked xylose to O-glucose on EGF repeats, and xyloside xylosytransferase 1 (XXTLT1) adds the second xylose to Xyl-Glc disaccharides on EGF repeats.
• POGLUT1 is overexpressed in some human myelodysplastic syndrome patients.
• POGLUT1 may also transfer Xyl directly to the EGF domain if the consensus sequence is C1-X-S-S-P/A-C2. Thus, it also exhibits POXYLT activity.