A Subunit of the Mammalian Oligosaccharyltransferase, DAD 1, Interacts with Mcl-1, One of the bcl-2 Protein Family

抄録

DAD 1 is a mammalian homologue of Saccharomyces cerevisiae Ost 2 p, a subunit of the oligosaccharyltransferase complex. Loss of its function induces apoptosis in hamster BHK 21 cells. By means of a two-hybrid method involving DAD 1 as bait, the C-terminal region of Mcl-1, one of the bcl-2 family, was isolated. Consistently, DAD 1 binds well to Mcl-1 in COS cells when overexpressed. On deletion analysis, the C-terminal domain of Mcl-1 containing BH² (bcl-2 homologous domain) was found to be essential for the interaction with DAD 1. On the other hand, the C-terminal half of DAD 1 was concluded to be essential for the interaction with Mcl-1. Surprisingly, a ΔC-DAD 1 mutant lacking only 4 amino acid residues from the C-terminus did not complement the tsBN 7 mutation, while it interacted well with Mcl-1. In contrast, ΔN-DAD 1 lacking 20 amino acid residues from the N-terminus still exhibited the ability to complement the tsBN 7 mutation. Thus, the C-terminus of DAD 1 was suggested to play an important role in N-linked glycosylation and to complement the tsBN 7 mutation. Mcl-1 may be required for the inhibition of apoptotic cell death caused by a loss of DAD 1.