Fig. 7. Treatment with HDAC inhibitor acetylates histone H4 protein. Chromatin histone protein was extracted from BE(2)-C and IMR-32 cells after 3 h of treatment with control or 0.1 mM TSA, and subject to immunoblot analysis with an anti-acetylated histone H4 antibody.

Fig. 8. HDAC inhibitor treatment does not up-regulate TG2 gene expression in normal, nonmalignant cells. Nonmalignant MRC-5 lung fibroblasts, MCF-10A1 breast epithelial cells, human umbilical vein endothelial cells (HUVEC), and primary human mammary epithelial cells, primary mouse lymphocytes from bone marrow, and, primary murine ganglia cells from para-vertebral ganglia were treated with control or 0.1 mM TSA for 6 or 24 h, followed by RNA extraction and semiquantitative competitive RT-PCR using transintron PCR primers for TG2 together with primers for the house-keeping gene b-actin as loading controls.

Fig. 9. TG2 siRNA knocks down TG2 gene expression in neuroblastoma and breast cancer cell lines. SHEP S1, MCF-7 and MDA-MB-468 cells were transfected with scrambled siRNA or TG2 siRNA for 8 h, followed by treatment with control or 0.1 mM TSA for 24 h. RNA and protein were extracted for competitive RT-PCR and immunoblot analysis of TG2 mRNA and protein expression.

Fig. 10. The role of TG2 in HDAC inhibitor-induced apoptosis. (a) Up-regulation of TG2 did not contribute to HDAC inhibitor-induced apoptosis. BE(2)-C and MCF-7 cells were transfected with scrambled or TG2 siRNA for 8 h, followed by treatment with 0.1 or 0.5 mM TSA respectively for 48 h. After fixation, cells were stained with the TUNEL reagent, examined under fluorescence microscope, and the percentage of TUNEL positive cells was quantified. (b) Up-regulation of TG2 did not contribute to HDAC inhibitor-induced up-regulation of BAX, or conformationally changed BAX. MCF-7 cells were transfected with scrambled (A-E) or TG2 siRNA (F) for 8 h, followed by treatment with control (A and C) or 0.5 mM TSA (B and D-F) for 48 h. After fixation, cells were incubated with mouse anti-BAX antibody 6A7 for conformationally changed, active BAX (A and B), rabbit anti-BAX antibody N-20 for total BAX (C and D), or combination of N-20 and 6A7 (E and F), followed by incubation with Alexa Fluor 488-conjugated donkey anti-rabbit antibody (shown by chevrons) and Alexa Fluor 594-conjugated donkey anti-mouse antibody (shown by arrows). Double-labeled cells showed yellow/orange staining (shown by arrowheads) (E and F).

Fig. 11. Validation of cDNA microarray data. The effect of N-Myc on its target gene expression was examined by semiquantitative competitive RT-PCR using transintron PCR primers for target gene fibronectin (FN1) and procollagen-lysine oxoglutarate dioxygenase2 (PLOD2) together with primers for the house-keeping gene b-actin as loading controls on mRNA from N-Myc over-expressing SHEP S1 or empty vector control SHEP EV cells.

Fig. 12. The role of N-Myc gene over-expression on TG2 transcription. (a) Tetracycline (TET) was withdrawn from SHEP TET-OFF cell culture medium to induce N-Myc gene over-expression for 48 h, followed by RNA extraction and RT-PCR analysis. (b) Normal nonmalignant MRC-5 lung fibroblasts and human mammary epithelial cells (HMEC) were transfected with constructs over-expressing c-Myc, N-Myc or empty vector respectively. Cellular protein was extracted 48 h after transfection and subjected to immunoblot analysis of c-Myc and N-Myc protein expression, with b-actin as loading controls.

Fig. 13. N-Myc siRNA up-regulates, and TG2 siRNA inhibits, TG2 gene transcription in neuroblastoma BE(2)-C and IMR-32 cells. BE(2)-C and IMR-32 cells were transfected with scrambled siRNA, N-Myc siRNA and/or TG2 siRNA for 48 h. The effect of siRNAs on the expression of N-Myc and TG2 was examined by competitive RT-PCR with primers targeting N-Myc, TG2 or b-actin, and by immunoblot with primary antibodies against TG2, N-Myc and b-actin.

Fig. 14. Schematic representation of the TG2, APEX-1 and nucleolin gene promoters. The diagrams of the TG2, APEX-1 and nucleolin gene promoters include: transcription start site (black arrow); Sp1 binding site (GC Box, white boxes); N-Myc-responsive element E-Box (gray boxes); position of DNA regions analyzed by quantitative ChIP and PCR (Amplicon, black arrow heads); exon-intron structure (black).

Fig. 15. N-Myc represses TG2 gene transcription by recruiting HDAC1 to the TG2 gene core promoter in IMR-32 cells. Dual cross-linking ChIP and quantitative PCR for TG2 and APEX-1 gene promoter were applied to IMR-32 cells. In each experiment, quantitative PCR was performed in triplicate for the tested DNA region of the TG2 and APEX-1 gene promoters. Fold enrichment of a given DNA region immunoprecipitated with anti N-Myc, MAX, Sp1 or HDAC1 antibodies was calculated as the ratio between the enrichment obtained with a specific antibody and that obtained with the preimmune serum. Results were the average of three independent dual cross-linking ChIP experiments. Error bars indicated standard error.

Fig. 16. HDAC1 only binds to TG2 gene core promoter. Dual cross-linking ChIP assay was performed on LAN-1 cells treated with control or TSA for 24 h, when a maximal transcriptional reactivation of TG2 was observed. PCR was carried out with primers targeting amplicon A, which was 1.6Kb up-stream of TG2 gene transcription start site.

Fig. 17. siRNA-mediated silencing of Sp1 induced TG2 expression in LAN-1 cells. (Left) Expression of Sp1 in LAN-1 cells treated with a specific Sp1 siRNA was determined by Western blotting. A scrambled siRNA was used as a control. (Right) Real time RT-PCR of TG2 mRNA expression after silencing of Sp1. The analysis was performed on two genes used as controls: hTERT regulated by Sp1 and on nucleolin not regulated by Sp1.