Jt. Collins et Wa. Dunnick, GERMLINE TRANSCRIPTS OF THE MURINE IMMUNOGLOBULIN GAMMA-2A GENE - STRUCTURE AND INDUCTION BY IFN-GAMMA, International immunology, 5(8), 1993, pp. 885-891
The switch in expression by B cells from IgM to IgG, IgE, or IgA is ac
complished by a DNA deletion. The deletion event is regulated, in that
specific cytokines direct the B cell to switch to one, or sometimes t
wo, of the six possible murine heavy chain genes. Prior to switch reco
mbination, cytokine treatment also induces the transcription of the co
nstant, switch, and upstream regions of the targeted heavy chain. Much
evidence indicates that IFN-gamma directs switch recombination to the
murine gamma2a gene. By developing probes specific for the gamma2a ge
ne, we demonstrate that IFN-gamma increases germline transcription of
this gene in both normal 8 cells and in the 18.81.A20 pre-B lymphoma.
We have obtained cloned copies of three different germline gamma2a tra
nscripts, each with a different donor splice site. We have also locate
d the 5' ends of these transcripts. The vast majority of the germline
gamma2a transcripts have a long first exon (> 700 bp), consistent with
observations by Severinson and her colleagues.