DAD1 Gene Research Articles

The highly conserved DAD1 protein involved in apoptosis is required for N-linked glycosylation.

The tsBN7 cell line is one of the temperature-sensitive mutants for cell proliferation which have been isolated from the BHK21 cell line derived from the golden hamster. It has a mutation in the DAD1 gene encoding a 12.5kDa highly conserved protein through evolution, and enters apoptosis at the restrictive temperature due to this mutation. DAD1 was recovered in light membrane fractions after differential centrifugation. It could not be released from the membrane, even by carbonate extraction, without a detergent. Upon digestion with proteinase K, both N and C terminal portions-but not the middle portions of DAD1- were released from the membrane. Thus, DAD1 appears to be an integral membrane protein in which both termini are located in the cytosol. DAD1 was localized in the endoplasmic reticulum. In accordance with a similarity to the yeast protein Ost2p, which is a subunit of the oligosaccharyltransferase, at the restrictive temperature, loss of DAD1 function caused a defect of N-linked glycosylation in tsBN7 cells resulting in apoptosis. However, tunicamycin, which is known to inhibit N-linked glycosylation did not induce apoptosis in either tsBN7 or BHK21 cells. tsBN7 cells have a defect in N-linked glycosylation caused by the loss of DAD1.

The DAD1 protein, whose defect causes apoptotic cell death, maps to human chromosome 14

Programmed cell death (PCD) is an important process in the development of animal embryos. Once this mechanism takes over, cells die by a process known as apoptosis in which the cells undergo a characteristic set of changes including cell shriveling and DNA breakdown. In the biological systems in which PCD has been investigated, it appears that specific pathways that lead to apoptosis exist. Some of the genes whose products act in these pathways have been characterized extensively in Caenorhabditis elegans (such as the gene ced-9) and in mammalian cells (such as Bc12). One gene whose protein product probably acts in a PCD pathway is the recently identified DAD1 gene. The DAD1 gene was shown to have a point mutation in tsBN7 cells that results in loss of DAD1 function at the nonpermissive temperature. The DAD1 gene encodes a 12.5-kDa protein that is expressed throughout the body at high levels. 14 refs., 1 fig.