6t7b
Structure of human Sox2 transcription factor in complex with a nucleosomeStructure of human Sox2 transcription factor in complex with a nucleosome
Structural highlights
Disease[SOX2_HUMAN] Defects in SOX2 are the cause of microphthalmia syndromic type 3 (MCOPS3) [MIM:206900]. Microphthalmia is a clinically heterogeneous disorder of eye formation, ranging from small size of a single eye to complete bilateral absence of ocular tissues (anophthalmia). In many cases, microphthalmia/anophthalmia occurs in association with syndromes that include non-ocular abnormalities. MCOPS3 is characterized by the rare association of malformations including uni- or bilateral anophthalmia or microphthalmia, and esophageal atresia with trachoesophageal fistula.[1] Function[H2B1K_HUMAN] Core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. Has broad antibacterial activity. May contribute to the formation of the functional antimicrobial barrier of the colonic epithelium, and to the bactericidal activity of amniotic fluid. [SOX2_HUMAN] Transcription factor that forms a trimeric complex with OCT4 on DNA and controls the expression of a number of genes involved in embryonic development such as YES1, FGF4, UTF1 and ZFP206 (By similarity). Critical for early embryogenesis and for embryonic stem cell pluripotency. May function as a switch in neuronal development. Downstream SRRT target that mediates the promotion of neural stem cell self-renewal (By similarity). Keeps neural cells undifferentiated by counteracting the activity of proneural proteins and suppresses neuronal differentiation (By similarity).[2] Publication Abstract from PubMed'Pioneer' transcription factors are required for stem-cell pluripotency, cell differentiation and cell reprogramming(1,2). Pioneer factors can bind nucleosomal DNA to enable gene expression from regions of the genome with closed chromatin. SOX2 is a prominent pioneer factor that is essential for pluripotency and self-renewal of embryonic stem cells(3). Here we report cryo-electron microscopy structures of the DNA-binding domains of SOX2 and its close homologue SOX11 bound to nucleosomes. The structures show that SOX factors can bind and locally distort DNA at superhelical location 2. The factors also facilitate detachment of terminal nucleosomal DNA from the histone octamer, which increases DNA accessibility. SOX-factor binding to the nucleosome can also lead to a repositioning of the N-terminal tail of histone H4 that includes residue lysine 16. We speculate that this repositioning is incompatible with higher-order nucleosome stacking, which involves contacts of the H4 tail with a neighbouring nucleosome. Our results indicate that pioneer transcription factors can use binding energy to initiate chromatin opening, and thereby facilitate nucleosome remodelling and subsequent transcription. Nucleosome-bound SOX2 and SOX11 structures elucidate pioneer factor function.,Dodonova SO, Zhu F, Dienemann C, Taipale J, Cramer P Nature. 2020 Apr;580(7805):669-672. doi: 10.1038/s41586-020-2195-y. Epub 2020 Apr, 22. PMID:32350470[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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