FIG. 1.

(A) The MMTV LTR, divided into U3, R, and U5 regions. The U3 region contains the transcription regulatory signals for the standard MMTV promoter that allows RNA initiation at the U3-R border. The approximate positions of the promoter-proximal (pNRE) and promoter-distal (dNRE) negative elements, as determined by reporter gene expression in transient-transfection assays, are shown. The probes used in this study include a 120-bp fragment that spans the pNRE and an oligonucleotide probe that includes an inverted repeat at the 3′ end of the 120-bp probe (see Materials and Methods). (B) Domain structures of SATB1 and CDP. The cut domains CR1, CR2, and CR3 and the homeodomain (HD) in CDP all can bind DNA independently, whereas the coiled-coil (CC) domain cannot (2, 18). An internal MAR domain, including the CR domains, contains the DNA-binding domain of SATB1 (40). Numbers indicate amino acid positions. CDP (the human protein) is known in other species as Cut (Drosophila), Clox (dogs), and Cux (mice) (1, 8, 53). In this paper, we use CDP to refer to proteins from all species.