4 - High Unwinding Capability of Matrix Attachment Regions and ATC-Sequence Context-Specific MAR-Binding Proteins

Abstract

This chapter describes the high unwinding capability of matrix attachment regions and ATC-sequence context-specific mar-binding proteins. Matrix attachment regions (MARs) play a role in tissue-specific gene expression. MARs associated with the immunoglobulin μ heavy chain locus are essential for the transcription of a rearranged μ gene in transgenic B lymphocytes. MAR activity was measured by its binding to the nuclear matrix and its effect on enhancer/promoter activities in vivo. It is suggested that special AT-rich binding protein 1 (SATB1) preferentially binds specific sites indirectly by recognizing an altered sugar-phosphate backbone structure that is dictated by the ATC sequence context. A MAR-binding protein is identified that associates with human breast carcinomas, but not with benign breast lesions or normal proliferating epithelial cells. The breast tumor MAR-binding protein is distinct from SATB1 but has similar binding recognition properties. It is suggested that base impairing regions of MARs may have multifunctional roles in transcription and replication, either as targets of regulatory proteins or as replication origins.