H2A.J is a poorly studied mammalian-specific variant of histone H2A. We used immuno histochemistry to study its localization in various human and mouse tissues. H2A.J showed cell-type
specific expression with a striking enrichment in luminal epithelial cells of multiple glands including
those of breast, prostate, pancreas, thyroid, stomach, and salivary glands. H2A.J was also highly ex pressed in many carcinoma cell lines and in particular, those derived from luminal breast and prostate
cancer. H2A.J thus appears to be a novel marker for luminal epithelial cancers. Knocking-out the
H2AFJ gene in T47D luminal breast cancer cells reduced the expression of several estrogen-responsive
genes which may explain its putative tumorigenic role in luminal-B breast cancer
