Js. Edmiston et Da. Lebman, A TRANSFORMING GROWTH-FACTOR-BETA REGULABLE RNA-BINDING PROTEIN INTERACTS SPECIFICALLY WITH GERMLINE IG ALPHA-TRANSCRIPTS, International immunology, 9(3), 1997, pp. 427-433
Isotype switching is presaged by the transcriptional activation of the
heavy chain class gene (CH) to which recombination will occur. As a r
esult, mRNA or germline transcripts from the unrearranged gene accumul
ate in the cytoplasm. Previous studies demonstrated that transforming
growth factor (TGF)-beta stimulated isotype switching to IgA in cultur
es of lipopolysaccharide (LPS)-stimulated murine B cells and increased
the stability of C-alpha mRNAs. The present study demonstrates that L
PS-stimulated B cells express a 45 kDa protein, l alpha BP, that speci
fically binds to germline a transcripts. Following addition of TGF-bet
a, the binding activity of this protein is significantly reduced. The
identification of a cytokine regulable RNA-binding protein that intera
cts with germline transcripts supports the idea that these transcripts
are involved in recombination and raises the possibility that RNA-pro
tein interactions play a role in regulating isotype switching.