Identification and characterization of a silkgland-related matrix association region in Bombyx mori

From DNA fragments in vivo attached to the nuclear matrix in silkglands of Bombyx mori 5th instar larvae, we have screened a matrix association region (M-AR), termed BmMAR1, by means of in vitro binding assay. BmMAR1 was iden tified to be specifically in vivo attached to the nuclear matrix only in th e silkglands, neither in other tissues nor in the silkworm cell line Bm5, i ndicating its silkgland-relatedness. This 1983-bp DNA fragment contains a 1 .1-kb core necessary for the effective in vitro binding although it is of r elatively lower A/T composition (61%) compared to the 5' and 3' flanking re gions (73 and 69%, respectively). Two degenerate sequences derived from Bm1 and L1Bm repetitive elements are located in the core region. BmMAR1 shares the widely considered typical MAR's features, DNA unwinding motif, A-box, T-box, H-box, replication origin, MAR recognition signature (MRS), the 90%A T box and Drosophila topoisomerase III consensus sequence. Furthermore we c ompared the occurrences of these patterns in BmMAR1 and some MARs from othe r organisms. (C) 2001 Elsevier Science B.V. All rights reserved.