Identification of an endogenous RNA transcribed from the antisense strand of the HFE gene

Hereditary haemochromatosis is an autosomal recessive disease which results in iron overload, and it is the most frequently inherited disorder in Cauc asian populations. The gene involved (HFE) has recently been identified, an d it encodes an MHC class I-like molecule. A 2.7 kb cDNA has been isolated, whereas the HFE gene expression is characterized by an almost ubiquitous m RNA of 4.1 kb in size. The difference between this transcript and the isola ted cDNA has not yet been explained. Thus, the 5' end of the HFE gene is st ill undefined and very little is known about the regulation of its expressi on. By searching this end, we isolated an antisense transcript originating from the same gene locus. Further investigations (rapid amplification of cD NA ends, RT-PCR experiments and dbEST screening) indicated that this RNA sp ans exon 1, exon 2, part of intron 1 of the HFE gene and similar to1 kb ups tream of it. This HFE antisense transcript is polyadenylated but displays n o open reading frame. A ribonuclease A protection assay definitively demons trated the biological existence of the HFE antisense RNA, which appears to be expressed in all of the tissues and cell lines tested. Furthermore, in v itro coupled transcription-translation experiments revealed that the HFE ex pression is decreased by this antisense RNA, indicating that it may play a critical role in the regulation of the HFE gene expression.