A CpG mutational hotspot in a ONECUT binding site accounts for the prevalent variant of hemophilia B Leyden.

Hemophilia B, or the "royal disease," arises from mutations in coagulation factor IX (F9). Mutations within the F9 promoter are associated with a remarkable hemophilia B subtype, termed hemophilia B Leyden, in which symptoms ameliorate after puberty. Mutations at the -5/-6 site (nucleotides -5 and -6 relative to the transcription start site, designated +1) account for the majority of Leyden cases and have been postulated to disrupt the binding of a transcriptional activator, the identity of which has remained elusive for more than 20 years. Here, we show that ONECUT transcription factors (ONECUT1 and ONECUT2) bind to the -5/-6 site. The various hemophilia B Leyden mutations that have been reported in this site inhibit ONECUT binding to varying degrees, which correlate well with their associated clinical severities. In addition, expression of F9 is crucially dependent on ONECUT factors in vivo, and as such, mice deficient in ONECUT1, ONECUT2, or both exhibit depleted levels of F9. Taken together, our findings establish ONECUT transcription factors as the missing hemophilia B Leyden regulators that operate through the -5/-6 site.

Treatment with the PARP-inhibitor PJ34 causes enhanced doxorubicin-mediated cell death in HeLa cells.

Adjuvant therapies can incorporate a number of different drugs to minimize the cardiotoxicity of cancer chemotherapy, decrease the development of drug resistance and increase the overall efficacy of the treatment regime. Topoisomerase IIα is a major target of many commonly used anticancer drugs, where cell death is brought about by an accumulation of double-strand DNA breaks. Poly (ADP-ribose) polymerase (PARP)-1 has been extensively studied for its role in the repair of double-strand DNA breaks, but its ability to add highly negative biopolymers (ribosylation) to target proteins provides a vast number of pathways where it can also be important in mediating cell death. In this study, we combine the classical topoisomerase IIα poison doxorubicin with the PARP inhibitor PJ34 to investigate the potentiation of chemotherapeutic efficiency in HeLa cells. We demonstrate that PJ34 treatment has the capacity to increase endogenous topoisomerase IIα protein by about 20%, and by combining doxorubicin treatment with PJ34, we observed a 50% improvement in doxorubicin-mediated cell death in HeLa cells. These results were correlated with the ribosylation of transcription factor specificity factor 1 after doxorubicin treatment, thereby altering its affinity for binding to known regulatory elements within the human topoisomerase IIα promoter. Taken together, these results highlight the synergistic potential of combining PARP inhibitors with classical topoisomerase IIα-targeting drugs.

You be the examiner!: "Model answers" that require critical thinking.

"You be the examiner!" is an online approach to providing students with immediate, readily accessible, and nonthreatening feedback on their understanding of key biochemical concepts. The feedback aims to affirm correct understanding and, where further study appears necessary, direct the student to the relevant sections of their textbook and/or lecturer-provided study notes. Rather than providing model answers to previous examination questions, "You be the examiner" asks the students to evaluate typical "student" answers to such questions. Instead of a single "correct" answer, students encounter a range of answers that they must assess for accuracy and appropriateness.

Modulation of DNA topoisomerase II alpha promoter activity by members of the Sp (specificity protein) and NF-Y (nuclear factor Y) families of transcription factors.

Topo IIalpha (topoisomerase IIalpha) is a major target of several commonly used anticancer drugs and is subject to down-regulation at the transcriptional level in some drug-resistant cell lines and tumours in response to chemotherapy. Clinical resistance to such drugs has been correlated with down-regulation of topo IIalpha at transcription in some drug-resistant cell lines and tumours. Putative binding sites for a variety of transcription factors, including Sp1 (specificity protein 1) and NF-Y (nuclear factor Y) have previously been identified in the topo IIalpha promoter, but their functional significance and interactions have not been described following exposure to anti-cancer drugs. The binding of these factors to specific putative regulatory elements in the topo IIalpha promoter was studied using electrophoretic-mobility-shift assays. Sp1 was found to bind strongly to both distal and proximal GC-rich elements and NF-Y to ICB1 (the first inverted CCAAT box). The functional significance of transcription-factor binding was studied using transient transfection of HeLa cells using a luciferase reporter driven by a 617-bp minimal promoter containing point mutations in putative regulatory elements. Sp1 and NF-Y were both found to be transcriptional modulators with activator or repressor functions depending on protein/DNA context. Moreover, a functional interaction between Sp1 and NF-Y bound at proximal elements was observed.

Reverse transcriptase-coupled quantitative real time PCR analysis of cell-free transcription on the chromatin-assembled p21 promoter.

BACKGROUND: Cell-free eukaryotic transcription assays have contributed tremendously to the current understanding of the molecular mechanisms that govern transcription at eukaryotic promoters. Currently, the conventional G-less cassette transcription assay is one of the simplest and fastest methods for measuring transcription in vitro. This method requires several components, including the radioisotope labelling of RNA product during the transcription reaction followed by visualization of transcripts using autoradiography. METHODOLOGY/PRINCIPAL FINDINGS: To further simplify and expedite the conventional G-less cassette transcription assay, we have developed a method to incorporate a reverse transcriptase-coupled quantitative real time PCR (RT-qPCR). By using DNA template depletion steps that include DNA template immobilization, Trizol extraction and DNase I treatment, we have successfully enriched p21 promoter-driven transcripts over DNA templates. The quantification results of RNA transcripts using the RT-qPCR assay were comparable to the results of the conventional G-less cassette transcription assay both in naked DNA and chromatin-assembled templates. CONCLUSIONS: We first report a proof-of-concept demonstration that incorporating RT-qPCR in cell-free transcription assays can be a simpler and faster alternative method to the conventional radioisotope-mediated transcription assays. This method will be useful for developing high throughput in vitro transcription assays and provide quantitative data for RNA transcripts generated in a defined cell-free transcription reaction.

Differential regulation of DNA repair protein Rad51 in human tumour cell lines exposed to doxorubicin.

Radiotherapy and chemotherapy often induce DNA double-strand breaks in both normal and malignant cells. The proteins involved in the repair of such lesions are central to cancer prognosis and treatment, as they can be overexpressed in many cancers, accelerating malignant transformation and increasing repair capacity, potentially leading to cellular resistance. If malignant cells can be selectively targeted repair proteins could also be candidates for targeted therapy. In this study, two keyplayers in eukaryotic DNA double-strand break repair, Rad51 and DNA-dependent protein kinase catalytic subunit, were analysed in noncancerous human breast cells (MCF12A) and the breast cancer cell lines (MDA MB 231 and MCF7) in response to treatment with doxorubicin. A cell cycle-independent increase in Rad51 protein levels (a recombinase involved in homologous recombination repair) was observed 24 and 48 h after treatment in MDA MB 231 and MCF12A when exposed to low levels of doxorubicin, whereas MCF7 cells displayed a continuous decrease in Rad51 protein with increasing drug concentration. DNA-dependent protein kinase catalytic subunit, which is involved in nonhomologous end joining of DNA lesions, remained unaltered under all conditions tested. Topoisomerase II-alpha protein, the primary target of doxorubicin, was upregulated at low concentrations of doxorubicin in all cell lines tested. Here we show that Rad51 protein levels can be differentially regulated in normal and malignant breast cell lines in response to doxorubicin, independent of cell cycle state. These observations have direct relevance to chemosensitivity and add an additional prognostic factor that could be taken into account when designing targeted therapeutic regimes.