Human Oct-1L isoform has tissue-specific expression pattern similar to Oct-2

5-Azacytidine Suppresses the Expression of Tissue-Specific Oct-1 Isoform in Namalwa Burkitt's Lymphoma Cell Culture

Overexpression of the transcription factor POU2F1 (Oct-1) increases the malignant potential of the tumor and determines the unfavorable prognosis for both solid and hematological cases of the disease in human carcinogenesis. The Oct-1 level determines the rate of development of the disease in acute myelodysplastic leukemia (AML), and a decrease in its expression significantly delays the development of leukemia in mice; however, a complete knockout of Oct-1 leads to the death of the animals. POU2F1 (Oct-1) is expressed as several isoforms transcribed from alternative promoters. They include both ubiquitous and tissue-specific isoforms. It was shown that in Burkitt’s lymphoma Namalwa cells 5-azacytidine specifically suppresses the expression of the tissue-specific isoform Oct-1L mRNA (level of Oct-1L is abnormally increased in these cells), while not causing changes in the amount of the ubiquitous isoform Oct-1A mRNA. These results show that it is possible to selectively reduce the transcription level of the Oct-1L isoform aberrantly expressed in human tumor cells.

Primate-specific stress-induced transcription factor POU2F1Z protects human neuronal cells from stress

The emergence of new primate-specific genes is an essential factor in human and primate brain development and functioning. POU2F1/Oct-1 is a transcription regulator in higher eukaryotes which is involved in the regulation of development, differentiation, stress response, and other processes. We have demonstrated that the Tigger2 transposon insertion into the POU2F1 gene which occurred in the primate lineage led to the formation of an additional exon (designated the Z-exon). Z-exon-containing primate-specific Oct-1Z transcript includes a short upstream ORF (uORF) located at its 5’-end and the main ORF encoding the Oct-1Z protein isoform (Pou2F1 isoform 3, P14859-3), which differs from other Oct-1 isoforms by its N-terminal peptide. The Oct-1Z-encoding transcript is expressed mainly in human brain cortex. Under normal conditions, the translation of the ORF coding for the Oct-1Z isoform is repressed by uORF. Under various stress conditions, uORF enables a strong increase in the translation of the Oct-1Z-encoding ORF. Increased Oct-1Z expression levels in differentiating human neuroblasts activate genes controlling stress response, neural cell differentiation, brain formation, and organogenesis. We have shown that the Oct-1Z isoform of the POU2F1/Oct-1 transcription factor is an example of a primate-specific genomic element contributing to brain development and cellular stress defense.

GSK3 Kinase Inhibitor, CHIR, Suppress Transcription of Tissue Specific POU2F1 Isoform in Burkitt Namalwa Lymphoma Cells

POU2F1 (Oct-1) is a transcription factor, the overexpression of which is found in many human malignant tumors; a significant increase in its level in cells determines the malignant potential of the tumor. POU2F1 is represented in cells by several isoforms that are transcribed from alternative promoters. In Burkitt's B-cell lymphoma Namalwa, the concentration of tissue-specific isoform Oct-1L is several times higher than in normal B cells. We tested the potential to inhibit the transcription of individual Oct-1 isoforms using the GSK3 kinase inhibitor CHIR, an aminopyrimidine derivative. We have shown that CHIR specifically affects the expression of the tissue-specific isoform Oct-1L, significantly reducing the level of mRNA and Oct-1L protein. However, CHIR does not change the amount of mRNA and protein of the ubiquitous isoform Oct-1A in Namalwa tumor cells. The results obtained show that it is possible to develop a system for selective inhibition of Oct-1 transcription factor isoforms in human cells to suppress drug resistance of tumor cells with a high POU2F1 content.

Pou2f1 and Pou2f2 cooperate to control the timing of cone photoreceptor production in the developing mouse retina

Multipotent retinal progenitor cells (RPCs) generate various cell types in a precise chronological order, but how exactly cone photoreceptor production is restricted to early stages remains unclear. Here, we show that the POU-homeodomain factors Pou2f1/Pou2f2, the homologs of Drosophila temporal identity factors nub/pdm2, regulate the timely production of cones in mice. Forcing sustained expression of Pou2f1 or Pou2f2 in RPCs expands the period of cone production, whereas misexpression in late-stage RPCs triggers ectopic cone production at the expense of late-born fates. Mechanistically, we report that Pou2f1 induces Pou2f2 expression, which binds to a POU motif in the promoter of the rod-inducing factor Nrl to repress its expression. Conversely, conditional inactivation of Pou2f2 in RPCs increases Nrl expression and reduces cone production. Finally, we provide evidence that Pou2f1 is part of a cross-regulatory cascade with the other temporal identity factors Ikzf1 and Casz1. These results uncover Pou2f1/2 as regulators of the temporal window for cone genesis and, given their widespread expression in the nervous system, raise the possibility of a general role in temporal patterning.

Differentiation of Monocytic Cells Is Accompanied by a Change in the Expression of the Set of Oct-1 Isoforms

Changes in the expression level of Oct-1A, Oct-1L, Oct-1X, and Oct-1Z isoforms and CD14 surface antigen during differentiation of HL-60 monocytic cells induced in vitro by dimethyl sulfoxide were studied, and the expression level of the four Oct-1 isoforms in vivo in human monocytes was determined.

The regulatory interplay between Oct-1 isoforms contributes to hematopoiesis and the isoforms imbalance correlates with a malignant transformation of B cells

Oct-1(POU2F1) is a DNA-binding transcription regulator and its level being highly increased in many human cancers. Oct-1 is present in the human cells as a family of functionally different isoforms which are transcribed from alternative promoters. Here, we have demonstrated that expression patterns of Oct-1 isoforms change during differentiation of hematopoetic progenitor cells (CD34+) (HPCs) to the B (CD19+) and T (CD3+) cells. While Oct-1L is expressed at a high level in the CD34+ HPCs, its expression level drops dramatically during the T-cell differentiation, although remains nearly the same in B-cells. We have described the novel human Oct-1R isoform which is conserved in mammals and is B cell-specific. Oct-1R was found in B cells, but not in HPCs. Oct-1R is transcribed from the same promoter as Oct-1L, another lymphocyte-specific isoform. Overexpression of Oct-1R and Oct-1L in the Namalwa cells leads to the repression of many genes involved in B-lymphocyte differentiation and signal transduction. Thus these isoforms may regulate the particular stages of development of normal B cells and maintain their proper differentiation status. However the extremely high level of Oct-1L isoform observed in the B-lymphoblast tumor cell lines indicated that the excess of Oct-L seem likely to considerably decrease the differentiation ability of these cells. Oct-1 may serve as a therapeutic target for many tumors, but it should be noted that in a tumor the content of a certain isoform Oct-1, rather than the total Oct-1 protein, can be increased.

Different N-terminal isoforms of Oct-1 control expression of distinct sets of genes and their high levels in Namalwa Burkitt's lymphoma cells affect a wide range of cellular processes

Oct-1 transcription factor has various functions in gene regulation. Its expression level is increased in several types of cancer and is associated with poor survival prognosis. Here we identified distinct Oct-1 protein isoforms in human cells and compared gene expression patterns and functions for Oct-1A, Oct-1L, and Oct-1X isoforms that differ by their N-terminal sequences. The longest isoform, Oct-1A, is abundantly expressed and is the main Oct-1 isoform in most of human tissues. The Oct-1L and the weakly expressed Oct-1X regulate the majority of Oct-1A targets as well as additional sets of genes. Oct-1X controls genes involved in DNA replication, DNA repair, RNA processing, and cellular response to stress. The high level of Oct-1 isoforms upregulates genes related to cell cycle progression and activates proliferation both in Namalwa Burkitt's lymphoma cells and primary human fibroblasts. It downregulates expression of genes related to antigen processing and presentation, cytokine-cytokine receptor interaction, oxidative metabolism, and cell adhesion, thus facilitating pro-oncogenic processes.

Increased level of Oct-1 protein in tumor cells modulates cellular response to anticancer drugs

The effect of overexpression of Oct-1 protein isoforms on the cell response to two anticancer drugs camptothecin and dexamethasone was studied. The effect of Oct-1 isoforms on regulated gene transcription was estimated by the difference in the level of mRNA in Burkitt's lymphoma cells (Namalwa line) untransfected and stably transfected with Oct-1 isoforms. The response to anticancer drugs of the Oct-1 target genes involved in the development of apoptosis depended, firstly, on the type of drug, secondly, on the concentration of Oct-1 in cells. and, thirdly, on the Oct-1 isoform with which these cells were transfected.

Involvement of transcription factor Oct-1 in the regulation of JAK-STAT signaling pathway in cells of Burkitt lymphoma

We studied the role of transcription factor Oct-1 in the regulation of expression of genes of the JAK-STAT signaling pathway in the Namalwa Burkitt's lymphoma cell line. Overexpression of Oct-1 isoforms (Oct-1A, Oct-1L, and Oct-1X) causes a decrease in the activity of four genes involved in the JAK-STAT signaling pathway-IFNAR2, STAT1, STAT2, and STAT4. As a result of our research, it was found that genes STAT2 and STAT4 are direct targets for Oct-1 protein.

Transcription factor Oct-1 stimulates the release of Mts1/S100A4 protein by the cancer cells

The effect of the transcription factor Oct-1 (POU2F1) on the expression of the tumor cell marker metastasin (Mts1/S100A4) was studied. Comparative analysis of various tumor lines showed no clear correlation between the expression level of Mts1/S100A4 and the content of Oct-1. However, at stable transfection of tumor cells with Oct-1A, Oct-1L, and Oct-1X isoforms we detected an elevated level of Oct-1, which stimulated Mts1/S100A4 secretion. These findings extend our understanding of the molecular mechanisms of the tumorigenic effect of Oct-1.

The level of the Phf10 protein, a PBAF chromatin-remodeling complex subunit, correlates with the Mts1/S100A4 expression in human cancer cell lines

Mts1 (S100A4) protein is a marker of metastatic tumor cells, which is associated with a poor diagnostic prognosis for cancer progression. Therefore, it is important to study the S100A4 gene expression. According to our preliminary data, PHF10, a PBAF remodeling complex component, can play an important role in the transcription regulation of the S100A4 gene. We studied the expression of S100A4 and the total PHF10 protein in some cell lines. We have found that, in the cell lines studied, the PHF10 expression is correlated with the S100A4 expression.

Oct-1 modifies S100A4 exchange between intra- and extracellular compartments in Namalwa cells and increases their sensitivity to glucocorticoids

S100A4, a small intra- and extracellular Ca(2+)-binding protein, is involved in tumor progression and metastasis with S100A4 level shown to be correlated with tumor cells metastatic potential. Simultaneously, Octamer transcription factor 1 (Oct-1) regulates a wide range of genes and participates in tumor cell progression with high Oct-1 level associated with a poor prognosis for different tumors. In this study, following the establishment of Oct-1 binding site, we used Burkit lymphoma B cells (Namalwa cells) which express different isoforms of Oct-1 (Oct-1A, Oct-1L and Oct-1X) to investigate the role of Oct-1 in S100A4 expression and sustaining intra- and extra-cellular S100A4 levels. As antitumor agents, we used dexamethasone which effect is mediated by the activation of intracellular glucocorticoid receptors and camptothecin which molecular target is nuclear DNA topoisomerase I (TOP1). We established that, firstly, the most significant increase in S100A4 gene expression has been demonstrated in the cells transfected with Oct-1A. Secondly, we have established that high level of Oct-1 and decreased intracellular S100A4 level decline the survival of Namalwa cells under dexamethasone treatment. Thirdly, we have shown that the tumor cells transformation by different Oct-1 isoforms retained those cells' sensitivity to the antitumor effect of combined dexamethasone and camptothecin. In contrast, in the non-transformed Namalwa cells, dexamethasone decreased the camptothecin effect on the cells survivorship, thus, emphasizing Oct-1 role in the regulation of cell response to different antitumor agents. The results identify a necessity to consider Oct-1 level for combined chemotherapeutic drug treatment.

New alternative promoter in regulation of the Oct-1 human gene transcription

For the first time, the presence of a new alternative promoter in the gene of the oct-1 transcription factor from which a previously unknown mRNA isoform Oct-1X, with 5'-terminus different from the previously described isoforms, was demonstrated. The nucleotide sequence of the Oct-1X cDNA was determined and the presence of a long open reading frame which starts with the first ATG codon of the second exon was demonstrated. A protein shortened on its N-terminus is assumed to be the product of a new mRNA isoform. Expression of the new isoform was studied in various human cell lines; the results indicate the ubiquitous nature of the Oct-1X expression. Therefore, in the work, the third alternative promoter of human oct-1 gene (earlier, a ubiquitous promoter U and an inducible tissue-specific promoter L were described) contributing to the fine regulation of mRNA isoform synthesis and formation of structural and functional diversity of Oct-1 protein isoforms in cells was revealed.

The essential role of Oct-2 in LPS-induced expression of iNOS in RAW 264.7 macrophages and its regulation by trichostatin A

This article reports on a study of the effect of trichostatin A (TSA), an inhibitor of histone deacetylase, on lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS) in RAW 264.7 macrophages and its underlying mechanisms. TSA pretreatment potently diminishes LPS-stimulated nitric oxide (NO) release and both mRNA and protein levels of iNOS in macrophages. The effects of TSA and LPS on transcription factors binding to two LPS-responsive elements within the iNOS promoter, one binding the NF-κB site and the other the octamer element, were investigated. Results show that TSA did not alter the LPS-activated NF-κB activity demonstrated by the nuclear translocation of p50 and p65 and by a NF-κB-driven reporter gene expression system. In addition, neither TSA nor LPS changed the expression of Oct-1, a ubiquitously expressed octamer binding protein. However, TSA suppressed the LPS-induced expression of Oct-2, another octamer binding protein, at both mRNA and protein levels. Chromatin immunoprecipitation assays revealed that binding of Oct-2 to the iNOS promoter was enhanced by LPS treatment; however, pretreatment with TSA resulted in loss of this binding. Moreover, forced expression of Oct-2 by transfection of pCG-Oct-2 plasmid restored the TSA-suppressed iNOS expression elevated by LPS stimulation, further indicating that Oct-2 activation is a crucial step for transcriptional activation of the iNOS gene in response to LPS stimulation in macrophages. This study demonstrates that TSA diminishes iNOS expression in LPS-treated macrophages by inhibiting Oct-2 expression and thus reducing the production of NO.

Autoregulation of Oct-1 gene expression is mediated by two octa-sites in alternative promoter

Transcription of the oct-1 gene is regulated by two alternative promoters: U promoter and L promoter located upstream of the exons 1U and 1L, respectively. The L promoter contains two octamer sequences of opposite orientation: proximal (ATTTGCAT) and distal (ATGCAAAT), showing high affinity toward the Oct proteins. Binding of the Oct-1 protein to the octa-sites located in the L promoter region has been confirmed in footprinting experiments. Dual luciferase assay using wild-type and mutated promoters have indicated that mutations in the proximal octa-site resulted in significant transcription enhancement both in myeloma cell line NS/0 and in fibroblast cell line 3T3 (about twofold and fivefold, respectively), whereas mutations in the distal site decreased the promoter activity (about 10% and 40%, respectively). Mutations in both octa-sites enhanced the effect and increased transcription to about fourfold in myeloma cell line NS/0 and about sixfold in fibroblast cell line 3T3. These results demonstrate that transcription of the oct-1 gene may be autoregulated by two octa-sites within the L promoter. Different function and interactive tissue-specific effect of distal and proximal octamer sequences can be suggested.

Identification of hippocampus-related candidate genes for Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial disease in which many genetic and environmental factors are involved. We performed an association study using 376 AD patients and 376 control subjects. We studied 35 single nucleotide polymorphisms in 35 genes that were significantly downregulated or upregulated only in the AD hippocampus compared with control and found that 9 single nucleotide polymorphisms were associated with AD. Our data indicated that single nucleotide polymorphisms could highly reflect differences in gene expression. Furthermore, an intronic polymorphism (+9943T/C) in POU2F1 was most significantly associated with AD (p = 0.0007). Our results suggest that POU2F1 is a candidate gene for AD.