tailieunhanh - Báo cáo Y học: Novel regulatory regions found downstream of the rat B29/Ig-b gene

To search for novel regulatory regions, we examined the features of chromatin structure in the rat B29/Ig-b gene and its flanking regions by determining DNase I hypersensitive sites (DHS) in plasmacytoma-derived Y3 cells. Six Y3 cellspecific DHS were detected at ), promoter, +, +, +, and + kb. The DHS at +, +, and + kb were present in the intergenic region between B29/Ig-b and growth hormone (GH) genes and were mapped inside conserved sequences in rat and humans. | Eur. J. Biochem. 269 1227-1236 2002 FEBS 2002 Novel regulatory regions found downstream of the rat 829 Ig-fi gene Ayano Komatsu Akira Otsuka and Masao Ono Life Science Course Department of Chemistry College of Science Rikkyo University Toshima-ku Tokyo Japan To search for novel regulatory regions we examined the features of chromatin structure in the rat B29 Ig-b gene and its flanking regions by determining DNase I hypersensitive sites DHS in plasmacytoma-derived Y3 cells. Six Y3 cellspecific DHS were detected at promoter and kb. The DHS at and kb were present in the intergenic region between B29 Ig-b and growth hormone GH genes and were mapped inside conserved sequences in rat and humans. In transient transfection into Y3 cells DNA containing the and DHS demonstrated six times more enhancing activity than B29 Ig-b promoter alone. Three intergenic DHS each possessed enhancing activity that was highest in the region. In the electrophoretic mobility shift assay a major band shift was demonstrated with Y3 nuclear extract and DNA containing the region with a conserved sequence. By footprint analysis 20 bases in the middle of the DNA were protected by Y3 nuclear extract in which the consensus binding site for the OCT family was present. Deletion of the footprinted region reduced enhancing activity to that of the B29 Ig-b promoter alone. The sequence responsible for the major band shift and transcriptional enhancing activity in the conserved region thus coincided with the 20-bp footprinted region. Keywords B29 Ig-b gene cell type-specific gene expression chromatin structure conserved regions DNase I hypersensitive site s . Along with membrane immunoglobulin mIg and Ig-a mb1 a B-cell-specific membrane protein B29 Ig-b is a component of the mIg receptor complex and belongs to the immunoglobulin superfamily 1 2 . Also called CD79b in humans B29 Ig-b is made of 228 amino acids in .