page_title: Pioneer factor
section_title: Active rearrangement
hierarchical_section_title: Pioneer factor / Active rearrangement
caption_attribution_description: English: Pioneer Factor opens the nucleosome in the chromatin.
context_page_description: Pioneer factors are transcription factors that can directly bind condensed chromatin. They can have positive and negative effects on transcription and are important in recruiting other transcription factors and histone modification enzymes as well as controlling DNA methylation. They were first discovered in 2002 as factors capable of binding to target sites on nucleosomal DNA in compacted chromatin and endowing competency for gene activity during hepatogenesis. Pioneer factors are involved in initiating cell differentiation and activation of cell-specific genes. This property is observed in histone fold-domain containing transcription factors and other transcription factors that use zinc finger for DNA binding.
  The eukaryotic cell condenses its genome into tightly packed chromatin and nucleosomes. This ability saves space in the nucleus for only actively transcribed genes and hides unnecessary or detrimental genes from being transcribed. Access to these condensed regions is done by chromatin remodelling by either balancing histone modifications or directly with pioneer factors that can loosen the chromatin themselves or as a flag recruiting other factors.
context_section_description: Pioneer factors can also actively affect transcription by directly opening up condensed chromatin in an ATP-independent process.  This is a common trait of fork head box factors (which contain a winged helix DNA-binding domain that mimics the DNA-binding domain of the linker H1 histone), and NF-Y (whose NF-YB and NF-YC subunits contain histone-fold domains similar to those of the core histones H2A/H2B).
caption: Opening of condensed chromatin by a pioneer factor to initiate transcription.   The pioneer factor binds to tightly packed chromatin and causes a nucleosomal rearrangement.  This new configuration allows space for other transcription factors to bind and initiate transcription.
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