Selective influence of Sox2 on POU transcription factor binding in embryonic and neural stem cells

by Tapan Kumar Mistri1, 2, 3, Devasia Arun George2, Lee Thean Chu2, Wei Ping Ng1, Florian Halbritter3, Ben Martynoga4, Simon R Tomlinson3, Ian Chambers3,#, Paul Robson2, 5,*, Thorsten Wohland1, 5, 6 x

1Department of Chemistry, National University of Singapore, Singapore, 2Developmental Cellomics Laboratory, Genome Institute of Singapore, Singapore. 3MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH16 4UU, Scotland, United Kingdom, 4Division of Molecular Neurobiology, MRC-National Institute for Medical Research, Mill Hill, London NW7 1AA, England, United Kingdom, 5Department of Biological Sciences and 6Centre for Bioimaging Sciences, National University of Singapore, Singapore.

EMBO Rep. 2015 Sep;16(9):1177-91. doi: 10.15252/embr.201540467. Epub 2015 Aug 11

Embryonic stem cell (ESC) identity is orchestrated by the co-operative activity of the transcription factors (TFs) Sox2 and the class V POU TF, Oct4 at composite Sox/Oct motifs. Neural stem cells (NSCs) lack Oct4 but express class III POU TF Oct4-homologs, Oct6, Brn1 and Brn2 as well as Sox2. This raises the question of how Sox2 interacts with POU TFs to selectively activate the ESC or NSC-specific transcriptional state. Here we show that Oct4 alone binds equally well to the Sox/Oct motif and to the octamer-containing ‘More palindromic Oct factor regulatory element’ (MORE). Sox2 binding selectively increases the affinity of Oct4 for the Sox/Oct motif. In contrast, Oct6 binds preferentially to the MORE, and is unaffected by Sox2. Genome-wide chromatin localisation in NSCs shows the most enriched motif for Oct6, Brn1 and Brn2 is in each case the MORE, with no evidence of a Sox/Oct motif. Moreover, MORE sub-types with C-A substitutions in positions 4 and 9, and a sub-type with a single base insertion between half-sites, are evident. These results suggest that in NSCs, co-operativity between Sox2 and class III POU TFs may not occur and that POU TF driven gene regulation uses predominantly the MORE cis architecture. Thus, distinct interactions between Sox2 and POU-TF subclasses distinguish pluripotent ESCs from multipotent NSCs, providing molecular insight into how Oct4 alone can convert NSCs to pluripotency.

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