A coding region determinant of instability

regulates levels of manganese superoxide dismutase mRNA

Previous data from our laboratory suggests that the regulation of the rat MnSOD gene may occur not only at the transcriptional, but quite possibly post-transcriptional level. To verify this hypothesis, we have attempted to identify regions within the rat MnSOD cDNA that may be functionally involved in regulating the stability of the mRNA. To localize the sequence elements involved in regulating MnSOD mRNA stability, we have employed the plasmid-based short-term promoter activation system, pBBB4.

Using a c-fos based promoter activation system we have identified an ~ 280 nucleotide fragment within the MnSOD mRNA coding region that, when fused to a rabbit b-globin gene, destabilizes the normally stable b-globin mRNA. This cis-directed destabilization phenomenon confers its effects independent of position an d stimulus.

The table below summarizes our data and illustrates the minimal element (181-463) of the coding region which confers the destabilizing activity.

Most importantly, the MnSOD coding region determinant functions when placed in the 3’ untranslated region of the b-globin transcript demonstrating its activity in the absence of ribosome transit. We feel that these data provide a mechanistic basis for both the basal, and stimulus-dependent post-transcriptional regulation of MnSOD.