Shen W F, Rozenfeld S, Lawrence H J, Largman C
Department of Medicine, San Francisco Veterans Affairs Medical Center and University of California, San Francisco, California 94121, USA.
J Biol Chem. 1997 Mar 28;272(13):8198-206. doi: 10.1074/jbc.272.13.8198.
Previous studies showed that the Hox homeodomain proteins from paralog groups 1-8 display cooperative DNA binding with the non-Hox homeodomain protein Pbx, mediated by a canonical YPWM. Although the Abd-B-like Hox proteins in paralogs 9-13 lack this sequence, Hoxb-9 and Hoxa-10 were reported to bind with Pbx1a to DNA. We show that these interactions require a tryptophan 6 amino acids N-terminal to the homeodomain. Binding site selection for Hoxb-9 with Pbx1a yielded ATGATTTACGAC, containing a novel TTAC Hox-binding site adjacent to a Pbx site. In the presence of Pbx1a, Hoxb-9 and Hoxa-10 bound to targets containing either TTAC or TTAT. These data extend previous findings that interactions with Pbx define a Hox protein binding code for different DNA sequences across paralog groups 1 through 10. Members of the 11, 12, and 13 paralogs do not cooperatively bind DNA with Pbx1a, despite the presence of tryptophan residues N-terminal to the homeodomain in Hoxd-12 and Hoxd-13. Hoxa-11, Hoxd-12, or Hoxd-13, in the presence of Pbx1a, selected a TTAC Hox site but lacking a Pbx1a site. These data suggest that Abd-B-like Hox proteins bind to a novel TTAC site and can be divided by their cooperative binding to DNA with Pbx1a.
先前的研究表明，旁系同源群1-8中的Hox同源结构域蛋白与非Hox同源结构域蛋白Pbx通过典型的YPWM介导协同结合DNA。尽管旁系同源群9-13中的Abd-B样Hox蛋白缺乏该序列，但据报道Hoxb-9和Hoxa-10可与Pbx1a结合到DNA上。我们发现这些相互作用需要在同源结构域N端6个氨基酸处有一个色氨酸。Hoxb-9与Pbx1a的结合位点筛选得到ATGATTTACGAC，其中包含一个与Pbx位点相邻的新型TTAC Hox结合位点。在Pbx1a存在的情况下，Hoxb-9和Hoxa-10可结合到含有TTAC或TTAT的靶标上。这些数据扩展了先前的研究结果，即与Pbx的相互作用定义了跨越旁系同源群1至10的不同DNA序列的Hox蛋白结合密码。尽管Hoxd-12和Hoxd-13的同源结构域N端存在色氨酸残基，但旁系同源群11、12和13的成员并不与Pbx1a协同结合DNA。在Pbx1a存在的情况下，Hoxa-11、Hoxd-12或Hoxd-13选择了一个TTAC Hox位点，但缺少Pbx1a位点。这些数据表明，Abd-B样Hox蛋白可结合到一个新型TTAC位点，并且可根据它们与Pbx1a协同结合DNA的能力进行区分。
