Range of HOX/TALE superclass associations and protein domain requirements for HOXA13:MEIS interaction

Abstract

AbdB-like HOX proteins form DNA-binding complexes with the TALE superclass proteins MEIS1A and MEIS1B, and trimeric complexes have been identified in nuclear extracts that include a second TALE protein, PBX. Thus, soluble DNA-independent protein-protein complexes exist in mammals. The extent of HOX/TALE superclass interactions, protein structural requirements, and sites of in vivo cooperative interaction have not been fully explored. We show that Hoxa13 and Hoxd13 expression does not overlap with that of Meis1-3 in the developing limb; however, coexpression occurs in the developing male and female reproductive tracts (FRTs). We demonstrate that both HOXA13 and HOXD13 associate with MEIS1B in mammalian and yeast cells, and that HOXA13 can interact with all MEIS proteins but not more diverged TALE superclass members. In addition, the C-terminal domains (CTDs) of MEIS1A (18 amino acids) and MEIS1B (93 amino acids) are necessary for HOXA13 interaction; for MEIS1B, this domain was also sufficient. We also show by yeast two-hybrid assay that MEIS proteins can interact with anterior HOX proteins, but for some, additional N-terminal MEIS sequences are required for interaction. Using deletion mutants of HOXA13 and HOXD13, we provide evidence for multiple HOX peptide domains interacting with MEIS proteins. These data suggest that HOX:MEIS interactions may extend to non-AbdB-like HOX proteins in solution and that differences may exist in the MEIS peptide domains utilized by different HOX groups. Finally, the capability of multiple HOX domains to interact with MEIS C-terminal sequences implies greater complexity of the HOX:MEIS protein-protein interactions and a larger role for variation of HOX amino-terminal sequences in specificity of function.

Homeobox gene methylation in lung cancer studied by genome-wide analysis with a microarray-based methylated CpG island recovery assay

“…However, by interacting with other transcription factors they can diversify their binding targets. Interacting partners for HOX proteins can be other homeodomain-containing factors (32)(33)(34)(35), and they synergistically govern the expression of downstream target genes. We noticed that nonclustered homeobox genes are also frequent targets of hypermethylation (Fig.…”

HOXA13 directly regulates EphA6 and EphA7 expression in the genital tubercle vascular endothelia

“…One possible explanation for this difference in binding site utilization is that HOX protein cofactors, such as the TALE class of DNA binding proteins, are also differentially expressed and can influence which DNA sequences are used by a particular HOX protein (reviewed by Moens and Selleri, 2006;Villaescusa et al, 2004;Williams et al, 2005;Erickson et al, 2006). For HOXA13, interactions with its cofactor, MEIS-1B, appears to be specific to the genitourinary region and may influence which of the DNA sequences are regulated by HOXA13 in this tissue (Williams et al, 2005). Alternatively, DNA accessibility may also vary in limb versus genitourinary chromatin, which could also account for the differential binding of HOXA13 to gene-regulatory sequences in a tissue-specific manner (Vashee et al, 1998;Kodadek, 1998).…”

PBX proteins: much more than Hox cofactors

“…Although these proteins are able to trigger very specific developmental programs, they all bind in vitro to a TAAT core sequence occurring approximately once every 500 base pair within the genome (Galant et al, 2002). Indeed, attempts to identify in vivo target genes by Chromatin Immunoprecipitation (ChIP) experiments, showed that these proteins bind DNA in a widespread fashion on TAAT sequences (Carr and Biggin, 1999, Walter et al, 1994, Williams et al, 2005. To explain this apparent paradox between the low DNA specificity of these proteins and their ability to trigger distinct developmental programs, it was suggested that the level of Hox proteins was more important than their nature, i.e., these proteins were so similar that they were interchangeable (Duboule, 2000).…”

“…While the majority of Hox monomers recognize a TAAT DNA core motif (Gehring et al, 1994), Hox-Pbx, Hox-Meis and Pbx-Meis heterodimers recognize larger motifs resulting in a higher affinity and specificity of DNA binding for these homeoproteins (Mann and Chan, 1996). Interestingly, recent data show that Hox/Meis interactions may extend to non-AbdB-like Hox proteins and that Meis proteins interact with different Hox groups using different interaction domains (Williams et al, 2005). The possible range of interactions demonstrated by these authors using a yeast twohybrid assay is expected to imply greater complexity in vivo, particularly in tissues that express multiple Meis isoforms.…”