RNA splicing of bacterial genes in eukaryotes

The presence of intervening sequences or introns in eukaryotic genes has be en known for more than 20 years, and the mechanisms underlying RNA splicing have been studied in depth both genetically and biochemically. In recent y ears, however, an increasing number of bacterial genes have been introduced into higher eukaryotes as important tools for genetic studies. Their gene products are frequently used as an indirect measure for cell type-specific promoter activity, as, for example, in the case of chloramphenicol acetyl t ransferase (CAT assay) or P-galactosidase, Here we show that RNA splicing o f two prokaryotic genes encoding site-specific DNA recombinases occurs in e ukaryotic cells. In one case, splicing is only observed after treatment of cells with the cytokine or interferon. We further demonstrate that mutating an intragenic donor splice site in a bacterial gene apparently activates a second, alternative splicing pathway. In conjunction with previous reports , our findings should also be regarded as a warning that splicing of bacter ial genes in higher eukaryotes is a more common phenomenon than presently r ecognized, which may be difficult to overcome and may cause problems in the interpretation of experimental results.