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Induction and Assessment of Class Switch Recombination in Purified Murine B Cells
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PTIP promotes chromatin changes critical for immunoglobulin class switch recombination

Jeremy A Daniel1, Margarida Almeida Santos, Zhibin Wang

  • 1Experimental Immunology Branch, National Cancer Institute, National Institutes of Health (NIH), Bethesda, MD 20892, USA.

Science (New York, N.Y.)
|July 31, 2010
PubMed

Programmed genetic rearrangements in lymphocytes require transcription at antigen receptor genes to promote accessibility for initiating double-strand break (DSB) formation critical for DNA recombination and repair. Here, we showed that activated B cells deficient in the PTIP component of the MLL3 (mixed-lineage leukemia 3)-MLL4 complex display impaired trimethylation of histone 3 at lysine 4 (H3K4me3) and transcription initiation of downstream switch regions at the immunoglobulin heavy-chain (Igh) locus, leading to defective immunoglobulin class switching. We also showed that PTIP accumulation at DSBs contributes to class switch recombination (CSR) and genome stability independently of Igh switch transcription. These results demonstrate that PTIP promotes specific chromatin changes that control the accessibility of the Igh locus to CSR and suggest a nonredundant role for the MLL3-MLL4 complex in altering antibody effector function.

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