n-Butyrate, a short chain fatty acid that is produced by colonic bacterial fermentation, is detectable in portal blood and induces differentiation in various human neoplastic cell lines. Earlier reports indicated ~20-fold induction in vitro by n-butyrate of the sialyltransferase that catalyzes terminal glycosylation of G(M3) ganglioside in HeLa and colon cancer cells. We previously isolated a 1.3-kilobase cDNA for a human β-galactoside α2,6- sialyltransferase, for which N-linked glycoproteins are the acceptors. We report here that treatment of Hep G2 cells with 5 mM n-butyrate for 24 h reduced β-galactoside α2,6-sialyltransferase mRNA levels by ~90%. Reductions in mRNA level were followed by ~75 and ~90% reductions, respectively, in specific β-galactoside α2,6-sialyltransferase enzyme activity after treatment for 24 and 36 h with 5 mM n-butyrate. However, in contrast with earlier reports of enhanced ganglioside synthesis in response to n-butyrate treatment, incubation of Hep G2 cells with n-butyrate did not alter the ganglioside pattern as assessed by thin layer chromatography of lipids extracted from treated cells. Nuclear run-on reactions indicated that the rate of transcription of β-galactoside, α2,6-sialyltransferase was not altered by treatment with 5 mM n-butyrate for 24 h, but the effects of this treatment on cytoplasmic levels of β-galactoside α2,6-sialyltransferase mRNA were largely negated by co-treatment with actinomycin D or cycloheximide. Therefore, our results show that n-butyrate reduces expression of mature β-galactoside α2,6-sialyltransferase mRNA by post-transcriptional mechanisms.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - 1992|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology