Conservation of 3' untranslated region elements in tammar wallaby (Macropus eugenii) TNF-alpha mRNA

To date, the only marsupial cytokine characterized at the molecular level is tumor necrosis factor- alpha , (TNF- alpha ) from the brushtail possum (Trichosurus vulpecula). Originally recognized as a potent tumor cell cytolytic factor, TNF- alpha is now also known to play a wide range of important roles in immunological and inflammatory processes. The derived primary structure of the brushtail possum TNF- alpha was found to be moderately similar to that of eutherian mammals with amino acid identities in the range of 56-58%. Intriguingly though, the brushtail possum cDNA was apparantly lacking the TA-rich octamer (TTATTTAT) motifs in its 3' untranslated region (3' UTR) which , in eutherian models, have been implicated as being important elements in the post-transcriptional regulation of a number of inflammatory mediators, such as TNF- alpha , by destabilizing the mRNA transcripts in unstimulated cells. Given the important role that these TA-rich elements are proposed to play in coordinating the regulation of a number of cytokine genes, it would be surprising if such a mechanism was absent in marsupials. However, because the canonical AATAAA polyadenylation signal is also absent from the brushtail possum sequence, this may simply reflect a cloning artifact. To address this question of whether TA-rich motifs play a role in the regulation of marsupial inflammatory mediators similar to that demonstrated in eutherians, we cloned the full-length TNF- alpha cDNA from another marsupial, the tammar wallaby (Macropus eugenii).