No abstract

Matrix attachment regions (MARs) are thought to separate chromatin into topologically constrained loop domains. A MAR located 5' of the human beta-interferon gene becomes stably base-unpaired under superhelical strain, as do the MARs flanking the immunoglobulin heavy chain gene enhancer; in both cases a nucleation site exists for DNA unwinding. Concatemerized oligonucleotides containing the unwinding nucleation site exhibited a strong affinity for the nuclear scaffold and augmented SV40 promoter activity in stable transformants. Mutated concatemerized oligonucleotides resisted unwinding, showed weak affinity for the nuclear scaffold, and did not enhance promoter activity. These results suggest that the DNA feature capable of relieving superhelical strain is important for MAR functions.

Rae1 alpha, Rae1 beta, and Rae1 gamma cDNAs isolated from retinoic acid-treated mouse embryonal carcinoma F9 cells encode cell surface proteins sharing partial homology with MHC class I molecules, and mRNAs corresponding to these cDNAs were detected exclusively in early mouse embryos, especially in the head region. To initiate studies on their roles, the rae1 alpha gene and the genomic DNAs covering the complete coding regions of the rae1 beta and rae1 gamma genes were isolated and their structures were analyzed. Although the coding regions of the three rae1 genes were highly homologous, the restriction map of the 5'-end region of the rae1 alpha gene differed from that of the rae1 beta and rae1 gamma genes. The rae1 family members were mapped by FISH on mouse chromosome 10A4 region. Genomic DNAs hybridizable with a Rae1 cDNA were not detected in rat and human. Rae1 genes were preferentially expressed in early mouse embryos, preferentially in the brain, and RAE1 proteins were anchored on the cell surface by a glycosyl phosphatidylinositol (GPI)-tail, a feature shared by important cell surface ligands.