Scaffold/matrix attachment region
![S/MAR-functions: constitutive and facultative. A chromatin domain with constitutive S/MARs at its termini (I). When functional demands require the specific translocation of the constituent gene to the matrix, facultative S/MARs responds to topological changes which are initiated by the association of transcription factors (TF) and supported by histone acetylation. Topological changes are propagated once the gene is pulled through the transcriptional machinery (II). Transcription is terminated (III) followed by dissociation of the transcrption complex (IV)](/Images/godic/202501/26/SMARs_facultative2654.png")
The term ´S/MAR´ (scaffold/matrix attachment region), otherwise called ´SAR´ (scaffold-attachment region), or ´MAR´ (matrix-associated region), are sequences in the DNA of eukaryotic chromosomes where the nuclear matrix attaches. As architectural DNA components that organize the genome of eukaryotes into functional units within the cell nucleus, S/MARs mediate structural organization of the chromatin within the nucleus. These elements constitute anchor points of the DNA for the chromatin scaffold and serve to organize the chromatin into structural domains. Studies on individual genes led to the conclusion that the dynamic and complex organization of the chromatin mediated by S/MAR elements plays an important role in the regulation of gene expression.