The identification and expression of heme oxygenase-2 alternative transcripts in the mouse

Murine heme oxygenase-2 (HO-2) cDNA sequences were determined through the assembly of mouse expressed sequence tag (EST) sequences using the rat HO-2 sequence as a template. The sequence analysis revealed two mRNA isoforms, probably arising through alternative splicing, which differed in their 5'-untranslated region (UTR), and were named HO-2a and HO-2b. One EST sequence included an extended 3'-UTR and suggested there may be a choice of poly-adenylation (poly-A) signal sequence. Reverse transcriptase polymerase chain reaction (PCR) suggested that HO-2a mRNA may be specifically expressed in the testis, while HO-2b mRNA was present in all tissues analysed. Furthermore, HO-2a and HO-2b transcripts were both found to include the extended 3'-UTR, but these transcripts were detected only in the testis. Northern analysis of a greater range of tissues confirmed the testis-specific expression of HO-2a mRNA and suggested that the transcripts which included the extended 3'-UTR were a small minority of the HO-2 mRNA population. These alternative murine HO-2 transcripts suggest that mechanisms such as mRNA transport, translational efficiency or mRNA turnover may be implicated in the regulation of HO-2 gene expression, most notably in the testis.