IL-7 functionally segregates the pro-B cell stage by regulating transcription of recombination mediators across cell cycle

• Published in: The Journal of immunology (1950) 2012-06, Vol.188 (12), p.6084-6092
• Main Authors: Johnson, Kristen, Chaumeil, Julie, Micsinai, Mariann, Wang, Joy M H, Ramsey, Laura B, Baracho, Gisele V, Rickert, Robert C, Strino, Francesco, Kluger, Yuval, Farrar, Michael A, Skok, Jane A
• Format: Article
• Language: English
• Subjects: Animals; B-Lymphocyte Subsets - cytology; B-Lymphocyte Subsets - immunology; B-Lymphocyte Subsets - metabolism; Cell Cycle - genetics; Cell Cycle - immunology; Cell Differentiation - genetics; Cell Differentiation - immunology; Flow Cytometry; Gene Rearrangement, B-Lymphocyte, Heavy Chain - genetics; Gene Rearrangement, B-Lymphocyte, Heavy Chain - immunology; Genes, RAG-1; Homeodomain Proteins - biosynthesis; Homeodomain Proteins - genetics; Homeodomain Proteins - immunology; In Situ Hybridization, Fluorescence; Interleukin-7 - immunology; Interleukin-7 - metabolism; Life Sciences; Mice; Microscopy, Confocal; Oligonucleotide Array Sequence Analysis; Precursor Cells, B-Lymphoid - cytology; Precursor Cells, B-Lymphoid - immunology; Precursor Cells, B-Lymphoid - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction - immunology; STAT5 Transcription Factor - immunology; STAT5 Transcription Factor - metabolism; Transcription, Genetic
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1200368

Ag receptor diversity involves the introduction of DNA double-stranded breaks during lymphocyte development. To ensure fidelity, cleavage is confined to the G(0)-G(1) phase of the cell cycle. One established mechanism of regulation is through periodic degradation of the RAG2 recombinase protein. However, there are additional levels of protection. In this paper, we show that cyclical changes in the IL-7R signaling pathway functionally segregate pro-B cells according to cell cycle status. In consequence, the level of a downstream effector of IL-7 signaling, phospho-STAT5, is inversely correlated with cell cycle expression of Rag, a key gene involved in recombination. Higher levels of phopho-STAT5 in S-G(2) correlate with decreased Rag expression and Rag relocalization to pericentromeric heterochromatin. These cyclical changes in transcription and locus repositioning are ablated upon transformation with v-Abl, which renders STAT5 constitutively active across the cell cycle. We propose that this activity of the IL-7R/STAT5 pathway plays a critical protective role in development, complementing regulation of RAG2 at the protein level, to ensure that recombination does not occur during replication. Our data, suggesting that pro-B cells are not a single homogeneous population, explain inconsistencies in the role of IL-7 signaling in regulating Igh recombination.