BP1 is a negative modulator of definitive erythropoiesis

A Potent Conformation-Constrained Synthetic Peptide Mimic of a Homeodomain Selectively Regulates Target Genes in Cells

DNA, as a target for therapeutic intervention, remains largely unexplored. DLX-4, a homeodomain containing transcription factor, and its spliced isoforms play crucial roles in many aspects of cellular biochemistry and important roles in many diseases. A smaller peptide mimicking the homeodomain of the transcription factor DLX-4 was designed and synthesized by suitable conjoining of its modified DNA-binding elements. The peptide binds to DLX-4 target sites on the regulatory region of the globin gene cluster with native-like affinity and specificity in vitro. When conjugated to cell penetrating and nuclear localization sequences, it upregulated some of the genes repressed by DLX-4 or its isoforms, such as β- and γ-globin genes in erythropoietin-induced differentiating CD34⁺ human hematopoietic stem/progenitor cells with high specificity by competing with the respective binding sites. Engineered peptides mimicking DNA-binding domains of transcription factors offer the potential for creating synthetic molecules for directly targeting DNA sites with high specificity.

DLX4 hypermethylation is a prognostically adverse indicator in de novo acute myeloid leukemia

Hypermethylation of distal-less homeobox 4 (DLX4) has been increasingly identified in several cancers. Our study was aimed to determine the role of DLX4 methylation in regulating DLX4 expression and further analyze its clinical significance in de novo acute myeloid leukemia (AML) patients. DLX4 methylation level was detected by real-time quantitative methylation-specific PCR and bisulfite sequencing PCR. Treatment with 5-aza-2'-deoxycytidine (5-aza-dC) was used for demethylation studies. Clinical significance of DLX4 methylation was obtained by the comparison between the patients with and without DLX4 methylation. DLX4 was significantly methylated in AML patients compared with controls (P < 0.001). DLX4 methylation was negatively associated with DLX7 (the shorter DLX4 isoform) (R = -0.202, P = 0.021) but not BP1 (the longer DLX4 isoform) (R = -0.049, P = 0.582) expression in AML patients. DLX7 and BP1 messenger RNA (mRNA) were significantly increased after 5-aza-dC treatment in leukemic cell lines THP1 and Kasumi-1. DLX4 methylated patients showed significantly higher frequency of U2AF1 mutation compared with DLX4 unmethylated patients (P = 0.043). Both all AML and non-M3 patients with DLX4 methylation presented significantly lower complete remission rate than those with DLX4 unmethylation (P = 0.001 and <0.001, respectively). DLX4 methylated cases had significantly shorter overall survival than DLX4 unmethylated cases among both all AML (P = 0.003), non-M3 AML (P = 0.001), and cytogenetically normal AML (P = 0.032). Multivariate analysis confirmed that DLX4 methylation was independent risk factor in both all AML and non-M3 patients. Our study indicates that DLX4 hypermethylation is negatively associated with DLX7 expression and predicts poor clinical outcome in de novo AML patients.

BP1 overexpression is associated with adverse prognosis in de novo acute myeloid leukemia

To investigate DLX4 isoforms expression and their clinical significance in acute myeloid leukemia (AML). DLX4 transcript variant 1 (BP1) expression was significantly up-regulated in AML patients compared with normal controls. However, DLX4 transcript variant 2 (DLX7) was significantly down-regulated in AML patients. Both in the overall AML and the non-M3 AML cohorts, those patients with high BP1 expression (BP1(high)) showed significantly lower rates of complete remission than those with low BP1 expression (BP1(low)). BP1(high) cases had significantly shorter overall survival than BP1(low) cases in the overall AML cohort, non-M3 AML, and cytogenetically normal AML (CN-AML). Multivariate analysis confirmed the independent prognostic value of BP1 expression among both the overall AML cohort and non-M3 AML as well as CN-AML patients. However, we did not observe the impact of DLX7 expression on prognosis in AML patients. Our study reveals that BP1 overexpression serves as an independent risk factor in de novo AML patients.

Screening of Transcription Factors Involved in Fetal Hemoglobin Regulation Using Phylogenetic Footprinting

Fetal hemoglobin (Hb F) is an important genetic modulator of the beta-hemoglobinopathies. The regulation of Hb F levels is influenced by transcription factors. We used phylogenetic footprinting to screen transcription factors that have binding sites in HBG1 and HBG2 genes’ noncoding regions in order to know the genetic determinants of the Hb F expression. Our analysis showed 354 conserved motifs in the noncoding regions of HBG1 gene and 231 motifs in the HBG2 gene between the analyzed species. Of these motifs, 13 showed relation to Hb F regulation: cell division cycle-5 (CDC5), myelo-blastosis viral oncogene homolog (c-MYB), transcription factor CP2 (TFCP2), GATA binding protein 1 (GATA-1), GATA binding protein 2 (GATA-2), nuclear factor erythroid 2 (NF-E2), nuclear transcription factor Y (NF-Y), runt-related transcription factor 1 (RUNX-1), T-cell acute lymphocytic leukemia 1 (TAL-1), YY1 transcription factor (YY1), beta protein 1 (BP1), chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), and paired box 1 (PAX-1). The last three motifs were conserved only in the noncoding regions of the HBG1 gene. The understanding of genetic elements involved in the maintenance of high Hb F levels may provide new efficient therapeutic strategies in the beta-hemoglobinopathies treatment, promoting reduction in clinical complications of these genetic disorders.

Fetal hemoglobin in sickle cell anemia: genetic studies of the Arab-Indian haplotype

Sickle cell anemia is common in the Middle East and India where the HbS gene is sometimes associated with the Arab-Indian (AI) β-globin gene (HBB) cluster haplotype. In this haplotype of sickle cell anemia, fetal hemoglobin (HbF) levels are 3-4 fold higher than those found in patients with HbS haplotypes of African origin. Little is known about the genetic elements that modulate HbF in AI haplotype patients. We therefore studied Saudi HbS homozygotes with the AI haplotype (mean HbF 19.2±7.0%, range 3.6 to 39.6%) and employed targeted genotyping of polymorphic sites to explore cis- and trans- acting elements associated with high HbF expression. We also described sequences which appear to be unique to the AI haplotype for which future functional studies are needed to further define their role in HbF modulation. All cases, regardless of HbF concentration, were homozygous for AI haplotype-specific elements cis to HBB. SNPs in BCL11A and HBS1L-MYB that were associated with HbF in other populations explained only 8.8% of the variation in HbF. KLF1 polymorphisms associated previously with high HbF were not present in the 44 patients tested. More than 90% of the HbF variance in sickle cell patients with the AI haplotype remains unexplained by the genetic loci that we studied. The dispersion of HbF levels among AI haplotype patients suggests that other genetic elements modulate the effects of the known cis- and trans-acting regulators. These regulatory elements, which remain to be discovered, might be specific in the Saudi and some other populations where HbF levels are especially high.

Fetal hemoglobin in sickle cell anemia

Fetal hemoglobin (HbF) is the major genetic modulator of the hematologic and clinical features of sickle cell disease, an effect mediated by its exclusion from the sickle hemoglobin polymer. Fetal hemoglobin genes are genetically regulated, and the level of HbF and its distribution among sickle erythrocytes is highly variable. Some patients with sickle cell disease have exceptionally high levels of HbF that are associated with the Senegal and Saudi-Indian haplotype of the HBB-like gene cluster; some patients with different haplotypes can have similarly high HbF. In these patients, high HbF is associated with generally milder but not asymptomatic disease. Studying these persons might provide additional insights into HbF gene regulation. HbF appears to benefit some complications of disease more than others. This might be related to the premature destruction of erythrocytes that do not contain HbF, even though the total HbF concentration is high. Recent insights into HbF regulation have spurred new efforts to induce high HbF levels in sickle cell disease beyond those achievable with the current limited repertory of HbF inducers.

Locus control region mediated regulation of adult beta-globin gene expression

Many genes residing in gene clusters and expressed in a differentiation or developmental-stage specific manner are regulated by locus control regions (LCRs). These complex genetic regulatory elements are often composed of several DNAse I hypersensitive sites (HS sites) that function together to regulate the expression of several cis-linked genes. Particularly well characterized is the LCR associated with the beta-globin gene locus. The beta-globin LCR consists of five HS sites that are located upstream of the beta-like globin genes. Recent data demonstrate that the LCR is required for the association of the beta-globin gene locus with transcription foci or factories. The observation that RNA polymerase II associates with the LCR in erythroid progenitor or hematopoietic stem cells which do not express the globin genes suggests that the LCR is always in an accessible chromatin configuration during differentiation of erythroid cells. We propose that erythroid specific factors together with ubiquitous proteins mediate a change in chromatin configuration that juxtaposes the globin genes and the LCR. The proximity then facilitates the transfer of activities from the LCR to the globin genes. In this article we will discuss recent observations regarding beta-globin locus activation with a particular emphasis on LCR mediated activation of adult beta-globin gene expression.

Distal-less homeobox transcription factors regulate development and maturation of natural killer cells

Natural killer (NK) cells constitute a subpopulation of lymphocytes that develop from precursors in the bone marrow (BM), but the transcriptional regulation of their development and maturation is only beginning to be understood, in part due to their relatively rare abundance, especially of developmental subsets. Using a mouse model in which NK cells are arrested at an immature stage of development, and a gene expression profiling approach, we uncovered transient normal NK cell expression of a homeobox transcription factor (TF) family, called Distal-less (Dlx), which had been primarily implicated in murine CNS, craniofacial, limb, and skin development. Our studies demonstrate that Dlx1, Dlx2, and Dlx3 are transiently expressed in immature Mac-1(lo) NK cells within the BM, with Dlx3 being the predominantly expressed member. These genes are expressed in a temporally regulated pattern with overlapping waves of expression, and they display functional redundancy. Expression is extinguished in fully mature splenic NK cells, and persistent expression of Dlx genes leads to functionally immature NK cells arrested at the Mac-1(lo) stage. Whereas conventional splenic NK cells develop but are arrested at an immature stage, there appears to be a complete failure to develop CD127(+) thymic NK cells when Dlx genes are persistently expressed. We also observed that T and B cells fail to develop in the context of persistent Dlx1 expression. Thus, these studies indicate that Dlx TFs play a functional role in lymphocyte development.

Prognostic significance of BP1 mRNA expression level in patients with non-small cell lung cancer

OBJECTIVES

To examine the association of BP1 mRNA level with tumor characteristics and clinical prognosis in non-small cell lung cancer (NSCLC) patients.

DESIGN AND METHODS

Tumor specimens from 98 NSCLC patients who underwent surgical resection were quantitatively determined for BP1 mRNA expression by real-time RT-PCR.

RESULTS

BP1 mRNA was expressed at significantly higher levels in tumors than in adjacent nontumorous tissues and normal lung samples. The level of BP1 transcript was significantly associated with tumor histological type and cell differentiation grade, but not related with other clinicopathological factors and p53 mutations. Patients with high BP1 mRNA expression had a poorer prognosis in terms of both disease-free survival (DFS) and overall survival (OS) rates. Additionally, BP1 mRNA expression level was an independent prognostic factor for DFS.

CONCLUSIONS

BP1 may be part of a pathway contributing to NSCLC development and/or progression. BP1 mRNA level could be a novel prognostic marker for NSCLC.

Expression level of beta protein 1 mRNA in Chinese breast cancer patients: a potential molecular marker for poor prognosis

Recent studies revealed high ectopic beta protein 1 (BP1) expression in breast cancer. Remarkably, up to 100% (18/18) of estrogen receptor (ER)-negative tumors and 89% (25/28) of tumors from African American women were BP1-positive. However, the role of BP1 in breast cancer development and its clinical significance still has not been well defined. In the present study, we analyzed the quantitative level of BP1 mRNA in breast carcinomas using real-time polymerase chain reaction and aimed to elucidate its association with tumor characteristics and patient prognosis. Our data showed that BP1 mRNA was expressed at significantly higher levels in tumors with lymph node metastasis, with a high histological grade, and in those that were of ER-negative status. Furthermore, overexpression of BP1 was significantly associated with poor outcome of patients harboring tumors with a high histological grade and negative ER. Using both in vitro and in vivo systems, we also showed that the transcript level of BP1 was positively correlated to the growth rate of breast tumor cells. Taken together, our results support the notion that BP1 might contribute to breast neoplastic transformation or tumor progression and suggest for the first time that BP1 mRNA level has potential as a prognostic predictor for breast cancer.