Molecular cloning and characterization of mouse EBAG9, homolog of a human cancer associated surface antigen: Expression and regulation by estrogen

We previously identified a human estrogen-responsive gene, EBAG9 (ER-bindin g fragment-associated antigen9) (Watanabe, T. ct at, Moi. Cell Biol 18, 442 -449, 1998). It was later reported as RCAS1 (receptor-binding cancer antige n expressed on SiSo cells) that induced apoptosis and suppressed the growth of several cells such as activated T cells (Nakashima, M. ct at, Not. Med 5, 938-942, 1999). Here, we have isolated both cDNA and genomic DNA of mous e EBAG9/RCAS1. Mouse EBAG9 gene spans about 30 kb in genomic DNA and consis ts of 7 exons. Mouse EBAG9 cDNA encodes a protein that contains the transme nbrane segment and coiled-coil domain. An alignment between the predicted m ouse and human EBAG;e shows a high degree of homology at the amino acid lev el (98%). Northern and Western blot analyses demonstrate that EBAG9 is expr essed in several tissues including the heart, brain, spleen, liver, kidney, and testis, and also in developing embryo. In the uterus, a target organ f or estrogen, the EBAG9 was shown to be upregulated in vivo by 17 beta -estr adiol. To determine the biological action of mouse EBAG;S, NIH3T3 fibroblas tic cells were incubated with recombinant EBAG9 protein, resulting in suppr ession of cell growth. These findings suggest that EBAG9 is an in vivo estr ogen-responsive gene that inhibits the cell growth. (C) 2001 Academic Press .