Identification and characterization of demethylase JMJD1A as a gene upregulated in the human cellular response to hypoxia

Hypoxia is commonly found in human solid cancers and serves as a selective environment for the survival of aggressive cancer cells and as protection from anti-cancer therapies. In addition to a shift to anaerobic metabolism, the cellular response to hypoxia includes cessation of cell division and/or cell death. These mechanisms have still not been defined. Identification of the members of hypoxia-induced growth arrest pathways remain incomplete. We have undertaken an expression microarray analysis of the cellular response to hypoxia in diverse cell lines. An identified cohort of genes is reliably upregulated in various cells in response to hypoxia, as validated by reverse-transcriptase polymerase chain reaction (RT-PCR). One of the upregulated targets corresponds to an expressed sequence tag encoded by JMJD1A (a gene also known as JHDM2A), which has been identified as a histone demethylase that regulates the transcription of androgen receptor targets. We confirm, by RT-PCR, the upregulation of JMJD1A after hypoxia and desferroxamine treatment in multiple cell lines. We also show that JMJD1A is predominantly, but not exclusively, a nuclear protein. Immunofluorescent staining of HeLa cells shows a shift of cytoplasmic JMJD1A into the nucleus on hypoxia treatment. Immunohistochemical staining has revealed that JMJD1A is widely expressed in tissues, even in cells that are not known to express the androgen receptor, and is significantly increased in smooth muscle cells upon hypoxia treatment.