Dual role of T1x3 as modulator of Prrxl1 transcription and phosphorylation

The proper establishment of the dorsal root ganglion/spinal cord nociceptive circuitry depends on a group of homeodomain transcription factors that includes Prodl, Brn3a and T1x3. By the use of epistatic analysis, it was suggested that T1x3 and Brn3a, which highly co-localize with Prrx11 in these tissues, are required to maintain Prodl expression. Here, we report two T1x3-dependent transcriptional mechanisms acting on Prrx11 alternative promoters, referred to as P3 and P1/P2 promoters. We demonstrate that (i) T1x3 induces the transcriptional activity of the TATA-containing promoter P3 by directly binding to a bipartite DNA motif and (ii) it synergistically interacts with Pmdl by indirectly activating the Prrx11 TATA-less promoters P1/P2 via the action of Bm3a. The T1x3 N-terminal domain 1-38 was shown to have a major role on the overall Tlx3 transcriptional activity and the C-terminus domain (amino acids 256-291) to mediate the Tlx3 effect on promoters P1/P2. On the other hand, the 76-111 domain was shown to decrease T1x3 activity on the TATA-promoter P3. In addition to its action on Prrx11 alternative promoters, T1x3 proved to have the ability to induce Prrx11 phosphorylation. The T1x3 domain responsible for Prrxl1 hyperphosphorylation was mapped and encompasses amino acid residues 76 to 111. Altogether, our results suggest that Tlx3 uses distinct mechanisms to tightly modulate Prixl1 activity, either by controlling its transcriptional levels or by increasing Prrx11 phosphorylation state. (C) 2014 Elsevier B.V. All rights reserved.