|Title||Distinct Elements Confer the Blocking and Bypass Functions of the Bithorax Fab-8 Boundary.|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Kyrchanova, O, Wolle, D, Sabirov, M, Kurbidaeva, A, Aoki, T, Maksimenko, O, Kyrchanova, M, Georgiev, P, Schedl, P|
|Date Published||2019 Sep 24|
Boundaries in the Drosophila bithorax complex (BX-C) enable the regulatory domains that drive parasegment specific expression of the three Hox genes to function autonomously. The four regulatory domains (iab-5, iab-6, iab-7 and iab-8) that control the expression of the Abdominal-B (Abd-B) gene are located downstream of the transcription unit and are delimited by the Mcp, Fab-6, Fab-7 and Fab-8 boundaries. These boundaries function to block crosstalk between neighboring regulatory domains. In addition, three of the boundaries (Fab-6, Fab-7 and Fab-8) must also have bypass activity so that regulatory domains distal to the boundaries can contact the Abd-B promoter. In the studies reported here, we have undertaken a functional dissection of the Fab-8 boundary using a boundary replacement strategy. Our studies indicate that the Fab-8 boundary has two separable sub-elements. The distal sub-element blocks crosstalk, but can not support bypass. The proximal sub-element has only minimal blocking activity but is able to mediate bypass. A large multiprotein complex, the LBC, binds to sequences in the proximal sub-element and contributes to its bypass activity. The same LBC complex has been implicated in the bypass activity of the Fab-7 boundary.