We have previously reported a differential transcriptional response by Iγ+ and Iγ- Ramos B cell subclones to CD40L signaling. Moreover, we found that the transcriptional response to both CD40L and CD40L plus EL-4 was greatest at the CHγ1 locus in both sets of subclones. To extend this work and begin to understand the nature of these differences, we have initiated experiments to assess the chromatin structure of the different Cγ loci in Ramos subclones prior to, and after CD40L and/or IL-4 stimulation. DNase1 sensitivity was measured across the Cγ regions using a 4 kb probe that cross-reacted with all four loci and extended from the Iγ through the Sγ region. Under conditions of no stimulation Iγ transcription, as assayed by RT-PCR, was undetectable from any γ locus in the subclone 3/3G5. We found that all four Cγ loci from unstimulated 3/3G5 cells were considerably more DNase1 sensitive when compared to the same loci in a Jurkat T cell line. Additionally, the Cγ1 locus from 3/3G5 cells was measurably more DNase1 sensitive compared to the Cγ2, 3, or 4 loci under all conditions tested. In contrast, the Cγ3 locus was highly resistant to DNase1 digestion even at the highest concentration of enzyme. These results indicate that the γ1 locus may be in a more open configuration, compared to the other γ loci, prior to T cell signaling. Observed differences in DNasel sensitivity at the different Cγ loci may reflect differences in accessibility and subclass-specific expression of Iγ transcripts in response to enviornmental cues.
|Published - Mar 20 1998
All Science Journal Classification (ASJC) codes
- Molecular Biology