Common Transcriptional Control Complexes of Murine CD21 and CD23 Suggests Stage Specific Repression (35.35)

Abstract

Abstract The expression of CD21 and CD23 is coincident in differentiating B cells during the T1 to T2 splenic transition stage. To define the factors regulating the expression of CD21 and CD23, we have used Chromatin Immunoprecipitation to map candidate transcription factors. Total naïve splenocytes showed constitutive binding of Oct1, NFATc3, YY1, NFkB-p52, PU.1, Pax5, E2A and RBP-Jk; to CD21 sequences (promoter and first intron) and NFkB-p52, Pax5, NFATc3, E2A and RBP-Jk to CD23 promoter sequences. Analysis of naïve T and B cell subsets showed constitutive binding of YY1, NFkB-p52, Pax5, Oct1 and NFATc3 proteins to CD21 sequences and NFkB-p52, Pax5, NFATc3 to CD23 promoter in B cells, but no specific binding of NFATc3 or Pax5 in T cell populations. Transcripts and protein for various NFAT species are present in splenic B and T cell (NFATc1, c2, c3, c4, NFAT5), but only a subset of NFAT proteins were defined to form constitutive complexes with the CD21 and CD23 gene sequences of resting T and B cells. The shared transcriptional control elements of CD21 and CD23 did not suggest an obvious means of alternative transcriptional regulation of these genes in marginal zone (MZ) B cells where CD21 cell surface expression and transcription are high and that of CD23 is absent or very low. These data suggest a model where MZ cells are derived directly from T1 splenic precursors. NIH-AI-24158 to JHW and NIH-AI-32223 to JJW