Organization, expression, and localization of the murine mdmx gene and pseudogene.

The mdmx gene is the first additional member of the mdm2 gene family to be isolated. It encodes a protein similar to MDM2 in several domains and also retains the ability to bind and inhibit p53 transactivation in vitro. However, mdmx does not appear to be transcriptionally regulated by p53. We have cloned and characterized the murine mdmx genomic locus from a 129 genomic library. The mdmx gene contains 11 exons, spans approximately 37 kb of DNA, and is located on mouse chromosome 1. The genomic organization of the mdmx gene is identical to that of mdm2 except at the 5' end of the gene near the p53 responsive element. Additionally, a pseudogene for mdmx was also identified that resides on the mouse X chromosome. Expression analysis of mdmx transcripts during mouse embryogenesis revealed constitutive and ubiquitous expression throughout development.