{'fraction_non_alphanumeric': 0.027642276422764227, 'fraction_numerical': 0.014634146341463415, 'mean_word_length': 5.217171717171717, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Histone 3 lysine 4 methylation during the pre-B to immature B-cell transition.

The relationship between chromatin modification and lymphocyte development is still poorly understood. Here we show a correlation between methylation of lysine 4 on histone 3 (H3-K4) and activation of several loci required for the pre-B cell to immature B-cell developmental transition. A critical step in this transition is the induction of V(D)J recombination at the Igkappa locus. Upon activation of Igkappa recombination, a >10-fold enrichment of both di- and trimethylated H3-K4 is observed at Jkappa targeting signals, but not at an analogous targeting signal in the T-cell receptor alpha locus or, surprisingly, at several Vkappa signals. However, H3-K4 methylation is restricted to the actively recombining fraction of Jkappa recombination targeting signals, consistent with a direct relationship between H3-K4 methylation and signal activity. Correlations between increased H3-K4 methylation and induction of transcription are also observed at some, but not all, loci where transcription is induced. H3-K4 methylation may therefore be a widely used but not universal means for controlling chromatin activity in this developmental transition.