scaffold associated region (SAR)

Introduction

Loci of DNA where the nuclear matrix attaches.

Site of attachment of topoisomerase 2 forming the base of loops associated with gene clusters.

Function

• constitute anchor points of DNA for the chromatin scaffold
• serve to organize chromatin into structural domains
• role in regulation of gene expression
• S/MAR separate a transcriptional domain) from its neighbors, but also & provide a nidus for the assembly of factors enabling transcriptional events within a transcriptional domain
• apparently an S/MAR may be either constitutive or facultative
• ~64,000 S/MAR (transcriptional domains) plus an additional ~10,000 S/MAR (replication foci) per cell nucleus

Structure

• occur at the flanks of transcribed regions, in 5 -introns, & at breakpoint cluster regions (BCR)
• no obvious consensus sequence

More general terms

• transcription factor binding site