Transcription regulator involved in inner cell mass and embryonic stem (ES) cells proliferation and self-renewal (PubMed:25825768). Imposes pluripotency on ES cells and prevents their differentiation towards extraembryonic endoderm and trophectoderm lineages. Blocks bone morphogenetic protein-induced mesoderm differentiation of ES cells by physically interacting with SMAD1 and interfering with the recruitment of coactivators to the active SMAD transcriptional complexes. Acts as a transcriptional activator or repressor. Binds optimally to the DNA consensus sequence 5'-TAAT[GT][GT]-3' or 5'-[CG][GA][CG]C[GC]ATTAN[GC]-3'. Binds to the POU5F1/OCT4 promoter (By similarity). Able to autorepress its expression in differentiating (ES) cells: binds to its own promoter following interaction with ZNF281/ZFP281, leading to recruitment of the NuRD complex and subsequent repression of expression. When overexpressed, promotes cells to enter into S phase and proliferation. Interacts with SMAD1 (PubMed:16801560). Interacts with SALL4 (PubMed:16840789). Interacts with ZNF281/ZFP281 (PubMed:21915945, PubMed:22988117). Interacts with PCGF1 (By similarity). Interacts with ESRRB; reciprocally modulates their transcriptional activities (PubMed:18957414). Interacts with NSD2 (PubMed:19483677). Not expressed in oocytes and spermatogonia (at protein level). Not expressed in many somatic organs, ovary, testis, fibroblast and hematopoietic cell lines. Expressed in the central portion of the morula, the inner cell mass (ICM) of the blastocyst, in embryonic stem (ES) and embryonic germ (EG) cells, in the epiblast between 6.5 and 7.5 dpc, in primordial germ cells (PGCs) between 7.75 and 12.5 dpc (at protein level). The expression in PGCs decreases in female germ cells that entered meiosis at 13.5 dpc and in male germ cells that entered mitotic arrest at 14.5 dpc (at protein level). Not expressed in unfertilized eggs or 2- or 8-cell-stage embryos (at protein level). Expressed in the central portion of the morula, the inner cell mass (ICM) of the blastocyst, in ES and EG cells, in the epiblast at 6 dpc and in PGCs of genital ridges between 11.5 and 12.5 dpc. Expression decreases with ES differentiation. By the transcription factor POU5F1 in ES cells that acts as a direct biphasic regulator: a steady-state concentration of POU5F1 up-regulated its expression, while an elevated concentration of POU5F1 down-regulated its expression. Up-regulated by the transcription factor FOXD3. Up-regulated in ES cells by transcription factors T (Brachyury) and STAT3. Down-regulated by p53 in response to DNA damage induced by ultraviolet light (UV) or doxorubicin. Down-regulated upon ES differentiation by mediating autorepression through interaction with ZNF281/ZFP281. Loss of pluripotency in both ICM and ES cells and differentiated into extraembryonic (parietal and visceral) endoderm lineage. 'Nanog' is derived from 'Tir nan Og' the mythologic Celtic land of the ever young. Belongs to the Nanog homeobox family.