The manufacturer’s instructions. IVT proteins were checked by western blot using an anti-HA antibody (Sigma). The sequences of the probes are (only the upper strand sequence is shown): E3:59-AGAAAAACTCCATCTAAAAAAAAAAAAAAAAAAAAAAAAAAACA-39. HCRII: 59-GACACATTAATCTATAATCAAATAC-39. NRDI: 59-GAAAGTGGAAATTCCTCTGAATAGAGAG-39.GST pull-down AssayGST and recombinant GST-fused proteins were expressed and purified following manufacturer’s instructions (Glutathione Sepharose 4B; GE Healthcare). Their purity, molecular mass and concentration were checked by SDS-PAGE and blue coomassie staining. GST pull-down assays were performed essentially as previously described [17].RT-PCR and in situ HybridizationsTotal RNA was extracted from embryos with the NucleoSpin RNAII kit (Macherey-Nagel) and in vitro reverse-transcribed using the GoScript Reverse Transcription System (Promega) and oligodT primers. To analyse the temporal expression of Xhmg-athook1, Xhmg-at-hook2 and Xhmg-at-hook3 by MedChemExpress Somatostatin-14 semiquantitative RTPCR, we used specific 59 primers for each of the three forms (XATH1SpecFw 59-GCTTCCAGCCTCTCCTTGGATCATATGCC-39; XATH2SpecFw 59-GCACAGAAGACCTGCTGCTGCTGACTAAG-39; XATH3SpecFw 59CCTGTGTCTTGTAGTCTTTGAAGG-39) and a shared 39 primer (XATHInt1R 59- CCCTCTTGGCCTTTTGGGAACCACAGTACCATTAG-39). In these PCRs we amplified RTgenerated cDNAs with 1 cycle at 94uC for 29and 30 cycles at 94uC for 300, 52uC for 300, 72uC for 500. As an internal control we used ornithine decarboxylase (ODC) primers [23]. For whole-mount in situ hybridization (WISH), Xenopus laevis embryos were staged and processed as previously described [15].Results HMGA and Multi AT-hook Factors in XenopusWe and others previously reported the identification of 23977191 laevis, based on homology with the genomic sequences of Xenopus tropicalis (see also description in the text). doi:10.1371/journal.pone.0069866.gmesh/hmg.html] and considering the biochemical data reported below, we named XHMG-AT-hook1 (Fig. 1A). The cloned Xhmg-at-hook1 cDNA sequence contains an ORF coding for a 327 aa protein.The manufacturer’s instructions. IVT proteins were checked by western blot using an anti-HA antibody (Sigma). The sequences of the probes are (only the upper strand sequence is shown): E3:59-AGAAAAACTCCATCTAAAAAAAAAAAAAAAAAAAAAAAAAAACA-39. HCRII: 59-GACACATTAATCTATAATCAAATAC-39. NRDI: 59-GAAAGTGGAAATTCCTCTGAATAGAGAG-39.GST pull-down AssayGST and recombinant GST-fused proteins were expressed and purified following manufacturer’s instructions (Glutathione Sepharose 4B; GE Healthcare). Their purity, molecular mass and concentration were checked by SDS-PAGE and blue coomassie staining. GST pull-down assays were performed essentially as previously described [17].RT-PCR and in situ HybridizationsTotal RNA was extracted from embryos with the NucleoSpin RNAII kit (Macherey-Nagel) and in vitro reverse-transcribed using the GoScript Reverse Transcription System (Promega) and oligodT primers. To analyse the temporal expression of Xhmg-athook1, Xhmg-at-hook2 and Xhmg-at-hook3 by semiquantitative RTPCR, we used specific 59 primers for each of the three forms (XATH1SpecFw 59-GCTTCCAGCCTCTCCTTGGATCATATGCC-39; XATH2SpecFw 59-GCACAGAAGACCTGCTGCTGCTGACTAAG-39; XATH3SpecFw 59CCTGTGTCTTGTAGTCTTTGAAGG-39) and a shared 39 primer (XATHInt1R 59- CCCTCTTGGCCTTTTGGGAACCACAGTACCATTAG-39). In these PCRs we amplified RTgenerated cDNAs with 1 cycle at 94uC for 29and 30 cycles at 94uC for 300, 52uC for 300, 72uC for 500. As an internal control we used ornithine decarboxylase (ODC) primers [23]. For whole-mount in situ hybridization (WISH), Xenopus laevis embryos were staged and processed as previously described [15].Results HMGA and Multi AT-hook Factors in XenopusWe and others previously reported the identification of 1315463 Xenopus cDNA sequences homologous to human HMGA2, namely Xlhmga2?(with two splicing variants Xlhmga2 and Xlhmga2 ) [7,15,16]. We performed additional database searches to look for other HMGA homologues in Xenopus. Despite extensive searches, and even though we found HMGA sequences in many Deuterostome and Protostome species, we could not find any sequence orthologous to mammalian HMGA1, either in Xenopus laevis or in the close species Xenopus tropicalis, whose draft genome sequence was announced to include 97.6 of known genes [31]. However, we identified overlapping cDNA sequences defining an ORF coding for a protein containing several AT-hooks that, following HMG nomenclature rules [http://www.nlm.nih.gov/Multi-AT-Hook Factors in XenopusFigure 1. XHMG-AT-hook proteins and organization of their transcripts and loci. (A) ClustalW alignment of XHMG-AT-hook protein isoforms. The amino acid sequences of the three different XHMG-AT-hook1-3 protein sequences (XATH1?) found in X. laevis and of the one (XATH3) found in X. tropicalis are shown. The conserved AT-hooks are shown in bold; internal repeats are boxed in different shades of yellow or brown respectively. The C-terminal region is boxed in orange. (B) Genomic organization of the Xhmg-at-hook locus in Xenopus tropicalis. The exon/intron organization is indicated together with the proposed mechanisms of generation of the different Xhmg-at-hook1-3 (XATH1-3) transcripts in Xenopus 23977191 laevis, based on homology with the genomic sequences of Xenopus tropicalis (see also description in the text). doi:10.1371/journal.pone.0069866.gmesh/hmg.html] and considering the biochemical data reported below, we named XHMG-AT-hook1 (Fig. 1A). The cloned Xhmg-at-hook1 cDNA sequence contains an ORF coding for a 327 aa protein.
