Targeting leukemic side population cells by isatin derivatives of nicotinic acid amide.

Side population (SP) cells mediate chemoresistance in leukemia. However, chemical inhibition approach to target SP cells has been poorly studied. Herein, we report the discovery of isatin derivatives of nicotinic acid amide as potent side population cell inhibitors. The selected derivatives showed superior potency over the reference drug verapamil. Furthermore, the treatment increased chemosensitivity and inhibited the cell proliferation on three different leukemic cell lines, K562, THP-1 and U937, suggesting that both SP and the bulk of leukemic cells are affected. Moreover, treatment with the most potent compound Nic9 reduced the expression of ABCG2, demonstrating that side population inhibition effect of the target derivatives is at least via ABCG2 inhibition. Importantly, the target derivatives induced erythrocyte/dendritic differentiation to leukemic cells mainly through Musashi/Numb pathway modulation.

Identification of a novel KCNQ1 mutation in a large Saudi family with long QT syndrome: clinical consequences and preventive implications.

Congenital long QT syndrome (LQTS) is an inherited potentially fatal arrhythmogenic disorder that is characterized by prolonged corrected QT (QTc) interval. Mutations in three genes (KCNQ1, KCNH2, and SCN5A) account for the majority of the cases. However, 10 other genes are now known to be implicated in LQTS. In this work, we describe the clinical and molecular analysis in a large Saudi family with LQTS. Screening KCNQ1, KCNH2, and SCN5A genes in the proband, who presented with syncope, led to the identification of a heterozygous mutation (p.H258P) in KCNQ1. An extended clinical and genetic screening of the family identified 11 other members who were carriers for this mutation. All identified carriers had prolonged QTc intervals; yet, only two were symptomatic. Screening the family members for three LQTS modifiers (rs4657139 and rs16847548 in NOS1AP and KCNE1-D85N) did not reveal a correlation with symptoms or QTc intervals. The electrocardiographic and molecular analysis stratified seven carriers at high risk of a cardiac event as they had a QTc of ≥500 ms and were carriers of a KCNQ1 mutation. Our work illustrates the importance of extended family screening in LQTS to identify silent carriers and hence adopt the most appropriate therapeutic and preventive intervention.

Organization and expression of two Arabidopsis DREB2 genes encoding DRE-binding proteins involved in dehydration- and high-salinity-responsive gene expression.

In plants, a cis-acting element, DRE/CRT, is involved in ABA-independent gene expression in response to dehydration and low-temperature stress. To understand signal transduction pathways from perception of the dehydration stress signal to gene expression, we characterized a gene family for DRE/CRT-binding proteins DREB2A and DREB2B in Arabidopsis thaliana. Northern analysis showed that both genes are induced by dehydration and high-salt stress. Organ-specific northern analysis with gene-specific probes showed that these genes are strongly induced in roots by high-salt stress and in stems and roots by dehydration stress. The DREB2A gene is located on chromosome 5, and DREB2B on chromosome 3. We screened an Arabidopsis genomic DNA library with cDNA fragments of DREB2A and DREB2B as probes, and isolated DNA fragments that contained 5'-flanking regions of these genes. Sequence analysis showed that both genes are interrupted by a single intron at identical positions in their leader sequence. Several conserved sequences were found in the promoter regions of both genes. The beta-glucuronidase (GUS) reporter gene driven by the DREB2 promoters was induced by dehydration and high-salt stress in transgenic Arabidopsis plants.

An Arabidopsis gene family encoding DRE/CRT binding proteins involved in low-temperature-responsive gene expression.

In higher plants, a cis-acting element, DRE/CRT, is involved in gene expression responsive to drought and low-temperature stress. To understand signal transduction pathways from the cold stress signal to gene expression, we characterized a gene family for DRE/CRT-binding proteins DREB1A and CBF1 in Arabidopsis thaliana. DREB1A and CBF1 were shown to be involved in low-temperature-responsive gene expression. We screened an Arabidopsis genomic DNA library with the cDNA fragment of DREB1A as a probe and isolated DREB1A and 2 related genes, DREB1B (= CBF1) and DREB1C. These were arrayed in the order B, A, C in an 8.7 kb region of Arabidopsis chromosome 4. Northern blot analysis using gene-specific probes showed that the 3 DREB1 genes are induced mainly by cold stress but not by osmotic stress in leaves, roots, and stems. Several conserved sequences were found in the promoter regions of all 3 genes. The beta-glucuronidase (GUS) reporter gene driven by the DREB1 promoters was induced at transcriptional level by low temperature in transgenic Arabidopsis plants.