Matrix attached regions, MARs

In situ hybridization experiments with several different fluorescent-labeled probes to DNA in human Interphase cells support the loop model shown in Figure 10-24. In these experiments, some probe sequences separated by millions of base pairs in linear DNA appeared reproducibly very close to one another in interphase nuclei from different cells (Figure 10-25). These closely spaced probe sites are postulated to lie close to specific sequences in the DNA, called scaffold-associated regions (SARs) or matrix-attachment regions (MARs), that are bound to the chromosome scaffold. SARs have been mapped by digesting histone-depleted chromosomes with restriction enzymes and then recovering the fragments that are bound to scaffold proteins. 

Describe the general organization of a eukaryotic chromosome. What structural role do scaffold associated regions (SARs) or matrix attachment regions (MARs) play Where are genes primarily located relative to chromosome structure ... 

Yanagisawa, J., Ando, J., Nakayama, J., Kohwi, Y. and Kohwi-Shigematsu, T. (19%). A matrix attachment region (MAR)-binding activity due to a pi 14 kilodalton protein is found only in human breast carcinomas and not in normal and benign breast disease tis.sues. Cancer Res. 56, 457-462. 

Model of eukaryotic gene structure and gene expression stages. BEs are boundary elements that bind proteins to prevent the enhancer effects on outside genes. MARs are matrix attachment regions. 

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