The pre‐B‐cell receptor induces silencing of VpreB and λ5 transcription

MJ Parker, S Licence, L Erlandsson, GR Galler… - The EMBO …, 2005 - embopress.org
MJ Parker, S Licence, L Erlandsson, GR Galler, L Chakalova, CS Osborne, G Morgan…
The EMBO journal, 2005embopress.org
The pre‐B‐cell receptor (pre‐BCR), composed of Ig heavy and surrogate light chain (SLC),
signals pre‐BII‐cell proliferative expansion. We have investigated whether the pre‐BCR
also signals downregulation of the SLC genes (VpreB and λ 5), thereby limiting this
expansion. We demonstrate that, as BM cells progress from the pre‐BI to large pre‐BII‐cell
stage, there is a shift from bi‐to mono‐allelic λ5 transcription, while the second allele is
silenced in small pre‐BII cells. A VpreB1‐promoter‐driven transgene shows the same …
The pre‐B‐cell receptor (pre‐BCR), composed of Ig heavy and surrogate light chain (SLC), signals pre‐BII‐cell proliferative expansion. We have investigated whether the pre‐BCR also signals downregulation of the SLC genes (VpreB and λ5), thereby limiting this expansion. We demonstrate that, as BM cells progress from the pre‐BI to large pre‐BII‐cell stage, there is a shift from bi‐ to mono‐allelic λ5 transcription, while the second allele is silenced in small pre‐BII cells. A VpreB1‐promoter‐driven transgene shows the same pattern, therefore suggesting that VpreB1 is similarly regulated and thereby defines the promoter as a target for transcriptional silencing. Analyses of pre‐BCR‐deficient mice show a temporal delay in λ5 downregulation, thereby demonstrating that the pre‐BCR is essential for monoallelic silencing at the large pre‐BII‐cell stage. Our data also suggest that SLP‐65 is one of the signaling components important for this process. Furthermore, the VpreB1/λ5 alleles undergo dynamic changes with respect to nuclear positioning and heterochromatin association, thereby providing a possible mechanism for their transcriptional silencing.
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