Oct-1 Gene Expression Research Articles

A Study to Explore the Role of IDH1 (R132) Mutation on Imatinib Toxicity and Effect of ABCG2/OCT1 Expression on N-Desmethyl Imatinib Plasma Level in Egyptian Chronic Myeloid Leukemia Patients.

Imatinib mesylate (IM) is the gold standard for treatment of Chronic Myeloid Leukemia (CML). This study aimed to gain more knowledge of the altered PK, pharmacogenetic factors, and gene expression leading to variable IM levels. Fifty patients with chronic phase-CML were enrolled in this study and divided as 25 responders and 25 non-responders (patients are directly recruited after response assessment). HPLC/MS/MS was used to determine trough and peak concentration of imatinib and N-desmethyl imatinib in the blood. PCR-RFLP technique was used to detect IDH1 gene mutation (R132). The median value of IM trough level was significantly higher, the P/T ratio was significantly lower and the α-1-acid glycoprotein (AGP) was significantly higher among responders compared to non-responders (P=0.007, 0.009 and 0.048, respectively). Higher N-desmethyl imatinib peak plasma concentration was observed with low mRNA expression of ABCG2 and OCT1 (P=0.01 and 0.037, respectively). IDH1 R132 gene mutation was associated with a significant increase in toxicities (P=0.028). In conclusion, IM trough level, P/T ratio and AGP was significantly higher in responders. In addition, ABCG2 and OCT1 gene expression may affect the interindividual PK variation. Although a prospective study with a larger patient population is necessary to validate these findings. IDH1 mutation is a predictor of increased toxicity with IM treatment.

Overexpression of the OCT-1 Gene Is a Biomarker Associated with Poor Outcomes in Diffuse Large B-Cell Lymphoma (DLBCL) - Data from a Retrospective Cohort from Latin America: Defining a Very High-Risk Clinical-Molecular Subgroup

Introduction: Diffuse large B-cell lymphoma (DLBCL) is the most frequent lymphoid malignancy, representing 30-40% of all non-Hodgkin's lymphomas (NHLs). They comprise a group of aggressive and heterogeneous neoplasms in terms of clinical presentation, response to therapy and prognosis. The OCT-1 gene is a member of the homodomain-POU family of transcriptional regulators of B-lymphoid differentiation. OCT-1 acts by controlling the expression of specific B-cell genes, such as BCL-2, a potent inhibitor of apoptosis that is essential for the differentiation of B-cells in the germinal center. These genes can be expressed in DLBCL, but the role of BCL-2 in its prognosis has been contradictory and the prognostic impact of the OCT-1 gene has not yet been tested in this lymphoma. Methods: In this observational, retrospective, single-center study, we investigated the prognostic impact of BCL-2 and OCT-1 gene expression in Brazilian patients with DLCBL treated with immunopolychemotherapy R-CHOP in a real-world context. The BCL-2 and OCT-1 genes were assessed in 78.5% (77/98) DLBCL patients, and the RNA for quantitative real-time PCR (qRT-PCR) was isolated from formalin-fixed and paraffin-embedded (FFPE) samples. The values obtained for gene expression were transformed into categorical variables according to their medians (6.27 for BCL-2 and 24.5 for OCT-1). The association between clinical and laboratory variables and results of gene expression was verified by the Fischer test. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Univariate analysis was performed using Cox's bivariate regression method and multivariate analysis using Cox multiple regression methodology. Results: The median age of the cohort was 54.5 years (15-84), 50% (49/98) were male, 49.4% (38/77) and 51.4% (40/77) showed expression of OCT-1 and BCL- 2 ≥ median, respectively. The clinical characteristics of the 98 Brazilian patients with DLBCL that comprised our cohort are summarized in Table 1. The overall response rate (ORR) in all patients was 68.4% (67/98), 65.3% (64/98) showed a complete response (CR), and 3.1% (3/98) showed partial response (PR), while 6.1% (6/98) were primary refractory. With a median follow-up of 3.77 years (95% CI: 3.2-4.1), the median overall survival (OS) was 5.43 years (95% CI: 2.2-NR) and the median progression-free survival (PFS) was 5.15 years (95% CI: 2.9-NR). The 5-year OS and PFS was 54.2% (42.2% -64.8%) and 52.0% (40.1-62.6%), respectively. In the univariate analysis OCT-1 ≥ median was associated with shortened OS (HR: 2.45, 95% CI: 1.21-4.96, p = 0.013) and PFS (HR: 2.27, 95% CI: 1.14-4.51, p = 0.019). Overexpression of BCL-2 was associated with worse PFS (HR: 2.00, 95% CI: 1.02-3.95, p = 0.043). Subgroup analysis showed that OCT-1 overexpression predominated in elderly individuals (≥ 60 years) in a statistically significant mode (29/38 cases - 76.3%, p = 0.029). It was also observed that overexpression of OCT-1 was associated with worse OS in the high-risk adjusted International Prognostic Index (aIPI) subgroup (p = 0.048) - Figure 1, and worse PFS in patients ≥ 60 years old (p = 0.025) - Figure 2. In the multivariate analysis, overexpression of OCT-1 was associated with poor PFS (HR: 2.22, 95% CI: 1.06-4.76, p = 0.035). Conclusion: In this study, we demonstrated that overexpression of the OCT-1 gene was an independent prognostic factor associated with adverse outcomes in Brazilian patients with DLCBL. We also show that in patients with unfavorable risk, such as the elderly and those with intermediate-high and high-risk IPI, overexpression of OCT-1 contributed to the identification of a very high-risk clinical-molecular subgroup, where the results with standard R-CHOP therapy are unsatisfactory, and they may benefit from intensified therapeutic strategies. Our results are preliminary and need to be validated in subsequent studies of prospective nature and with an expanded sample. Disclosures No relevant conflicts of interest to declare.

OCT1 gene Expression Is an Independent Prognostic Factor in Diffuse Large B Cell Lymphoma

Background: Transcription factors associated with the POU domain modulate the expression of several genes of B lymphoid differentiation, including the IgH. The study of these factors allowed to better understand the pathogenesis of lymphomas and to establish the lineage and the differentiation stage of the malignant cell. The silencing of OCT1 in tumor cell lines reduced its malignant transformation, but its ectopic expression enhanced the tumorigenesis ability. However, few studies has been evaluated the role of the OCT1 gene expression in lymphoma. In this study we assessed the impact of the OCT1 gene expression in the survival of patients with Diffuse Large B Cell Lymphoma (DLBCL).Methods: From January 2006 to January 2011 were evaluated 77 patients with DLBCL treated with R-CHOP at Clinical Hospital and Cancer Institute of Sao Paulo University. The RNA was extracted from the paraffin block at lymphoma diagnosis and gene expression analysis was performed by relative quantification method by Real-Time PCR (qRT-PCR). After the data normalization using two different reference genes, the median expression of OCT1 was obtained. The overall survival (OS) and progression-free survival (PFS) were estimated by the Kaplan-Meier method. The relative risks were obtained by Cox regression bivariate intervals with 95% of confidence. The significance level of 5% was accepted and the IBM SPSS Statistics software version 20.0 was used.Results: Patients showing OCT1 expression < the median presented higher OS (p = 0.010) and PFS (p = 0.016) than patients with OCT1 expression ≥ median with a hazard rate (HR) for OS and PFS of 2.45 and 1.14, respectively. In multivariate analysis the PFS was also higher in patients with OCT1 expression < the median (p = 0.035). The stratification by the international prognostic index (IPI) and age showed that the expression of OCT1 < median showed a statistically significant difference in the OS (p = 0.048) in IPI intermediate-high (HI) and high (HR) patients (p = 0.048), with a HR of 2.32 in HI plus HR group. The PFS (p = 0.025) and OS (p = 0.025) were lower in patients ≥ 60 years and OCT1 expression ≥ the median.Conclusion: Our data suggest that the expression of OCT1 showed a predictive prognostic impact in DLBCL independently of IPI. Patients with lower expression of OCT1 presented a better OS and PFS. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Glucocorticoid receptor regulates organic cation transporter 1 (OCT1, SLC22A1) expression via HNF4α upregulation in primary human hepatocytes

BackgroundOrganic cation transporter 1 (OCT1, SLC22A1) is a membrane transporter that is important for therapeutic effect of the antidiabetic drug metformin. Its liver-specific expression in hepatocytes is strongly controlled by hepatocyte nuclear factor-4α (HNF4α). HNF4α expression and transcriptional activity have been demonstrated to be augmented by glucocorticoid receptor (GR) in human hepatocytes and rodent livers. MethodsIt was examined whether GR activation indirectly induces OCT1 gene expression via HNF4α up-regulation in primary human hepatocytes.We also examined which other transcription factors are involved in OCT1 gene expression and whether they are regulated by dexamethasone using qRT-PCR and gene reporter assays. ResultsWe found that dexamethasone significantly up-regulates OCT1 mRNA and protein in normal primary human hepatocytes, but not in hepatocyte-derived tumor cell lines HepG2 and MZ-Hep1. Consistently, we observed that HNF4α is induced by dexamethasone in primary human hepatocytes, but not in hepatocyte tumor-derived cell lines. Viral transduction of MZ-Hep1 cells with the expression constructs for HNF4α, CCAAT/enhancer binding proteins β (C/EBPβ) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α) demonstrated significant roles of the transcription factors in OCT1 gene regulation.We found that expression of OCT1 mRNA in human livers significantly correlates with C/EBPβ and HNF4α mRNAs expression and that C/EBPβ co-transfection stimulates OCT1 gene reporter construct in HepG2 cells. Nevertheless, neither C/EBPβ nor PGC1α were upregulated in human hepatocytes by dexamethasone. ConclusionWe can conclude that GR-induced expression of HNF4α may contribute to indirect OCT1 gene up-regulation by dexamethasone in primary human hepatocytes, but not in hepatocyte-derived tumor cell lines.

Effect of Inflammation on Molecular Targets and Drug Transporters

Inflammation, the host's response to infection and injury, is associated with altered expression of genes such as metabolizing enzymes, transporters, receptors and plasma proteins. The purpose of the present work was to characterize the effect of inflammation on selected molecular targets and transporters that affect drugs' action and disposition. We have used rats with adjuvant arthritis (AA), an animal model of chronic inflammation. The AA group received 0.2 ml of 50 mg ml-1 Mycobacterium butyricum suspended in squalene into the tail base. On day 12, the rats were euthanized and their organs (heart, liver, kidneys and intestine) excised. Expression of Cav1.2, β1-AR, β2-AR, α1A-AR, Nav1.2, Nav1.6, Kv1.5, Kv2.1, Kv3.1, oatp1a1, oatp1a5, oatp1b2, oatp2b1, oatp4a1, oat2, oat3, oct1, mdr1a, bsep, mrp1, mrp3, mrp6, IL-1α, IFN-γ, iNOS, MCP-1, IL-10, Cox-1 and Cox-2 were determined by real time polymerase chain reaction (RT-PCR). Inflammation resulted in a significant reduction of oct1, oatp4a1 and mrp1 gene expression in the liver and oatp2b1, mrp6 and bsep gene expression in the kidney. Oatp4a1 and mdr1a were found to be significantly upregulated in rat heart. In conclusion, inflammation alters the gene expression of some mediators and drug transporters that can influence the behavior of drugs in the body and contribute to therapeutic failure.

OCT1 Expression in Adipocytes Could Contribute to Increased Metformin Action in Obese Subjects

OBJECTIVEMetformin has been well characterized in vitro as a substrate of liver-expressed organic cation transporters (OCTs). We investigated the gene expression and protein levels of OCT-1 and OCT-2 in adipose tissue and during adipogenesis and evaluated their possible role in metformin action on adipocytes.RESEARCH DESIGN AND METHODSOCT1 and OCT2 gene expressions were analyzed in 118 adipose tissue samples (57 visceral and 61 subcutaneous depots) and during human preadipocyte differentiation. To test the possible role of OCT1 mediating the response of adipocytes to metformin, cotreatments with cimetidine (OCT blocker, 0.5 and 5 mmol/l) and metformin were made on human preadipocytes and subcutaneous adipose tissue (SAT).RESULTSOCT1 gene was expressed in both subcutaneous and visceral adipose tissue. In both fat depots, OCT1 gene expression and protein levels were significantly increased in obese subjects. OCT1 gene expression in isolated preadipocytes significantly increased during differentiation in parallel to adipogenic genes. Metformin (5 mmol/l) decreased the expression of lipogenic genes and lipid droplets accumulation while increasing AMP-activated protein kinase (AMPK) activation, preventing differentiation of human preadipocytes. Cotreatment with cimetidine restored adipogenesis. Furthermore, metformin decreased IL-6 and MCP-1 gene expression in comparison with differentiated adipocytes. Metformin (0.1 and 1 mmol/l) decreased adipogenic and inflammatory genes in SAT. OCT2 gene expression was not detected in adipose tissue and was very small in isolated preadipocytes, disappearing during adipogenesis.CONCLUSIONSOCT1 gene expression and protein levels are detectable in adipose tissue. Increased OCT1 gene expression in adipose tissue of obese subjects might contribute to increased metformin action in these subjects.

Candidate Pathway Approach of Single Nucleotide Polymorphism On Imatinib Transport/Metabolism Pathway and DNA Repair Enzyme Pathway Associated with Response and Resistance to Imatinib Therapy in Chronic Myeloid Leukemia.

Abstract 3284Poster Board III-1 Purpose:Imatinib resistance is a major cause of imatinib treatment failure in chronic myeloid leukemia (CML) patients. In our previous study (Clin Cancer Res, 2009, 15(14):4750–8), SNP markers in the pathways of imatinib metabolism / transport could predict the response and resistance of imatinib therapy in CML. It has been known that organic cationic transporter-1 gene (OCT1, SLC22A1) is regulated by HNF4A (hepatocyte nuclear factor 4-alpha) or by PPARA (peroxisomal proliferators-activated receptor alpha) or PPARD (PPAR-delta).In addition, DNA repair machinery such as NER (nucleotide excision repair) or DSB (double strand break) repair pathway, plays an important role in the action mechanism of imatinib, in which ERCC5 (excision repair cross-complementing rodent repair deficiency, complementation group 5), or XRCC4 (X-ray repair complementing defective repair in Chinese hamster cells 4), were involved.The response to imatinib therapy in chronic myeloid leukemia (CML) is various according to inter-individual variation of drug delivery or metabolism. Thus, the current study investigated SNPs in the candidate genes involved in the imatinib transport/metabolism pathway and DNA repair enzyme pathway, and its association with clinical outcomes following imatinib therapy in CML patients. Methods:In the current study, we investigated 81 SNPs markers involved in the pathways of imatinib transport/metabolism pathway (n=62; ABCB1, ABCG2, CYP1A2, CYP2C9, CYP2C18, CYP2C19, CYP3A4, CYP3A5, AGP, OCT1, PPARA, PPARD, HNF4A) and DNA repair enzyme pathway (n=19; ERCC1/2/4/5, XRCC1/2/4/5). Total of 187 CML patients treated at the Samsung Medical Center, Chonnam National University Hwasun Hospital, or Kyungpook National University Hospital, Korea, were enrolled into the study. The DNAs from peripheral blood samples were genotyped with MALDI-TOF based technique (Sequenom). Results:Among the SNP markers involved in imatinib transport/ metabolism pathway, HNF4A (rs3212172) was significantly associated with high risk of loss of response (LOR; p<0.001) or treatment failure (p=0.013). CYP1A2 (rs762551) was significantly associated with high risk of LOR (p<0.001) or treatment failure (p=0.035). In addition, ERCC5 (rs17655) showed significant association with response (p=0.036 for complete cytogenetic response [CCR], 0.024 for major molecular response [MMR]) or with resistance (p=0.05 for LOR, 0.025 for treatment failure), while XRCC4 (rs963248) showed significantly consistent association with response to imatinib (p=0.025 for major cytogenetic response [MCR], 0.032 for CCR, 0.008 for MMR, and 0.06 for complete molecular response [CMR]). External validation is now ongoing and the result will be presented in the meeting. Conclusions:The current study suggested that SNP marker on HNF4A gene, regulator of OCT1 gene expression, could predict the risk of resistance to imatinib therapy, and that SNP markers on ERCC5 or XRCC4, involved in the NER and DSB repair pathway, also could predict the response to imatinib therapy, suggesting a potential involvement of DNA repair machinery in the action mechanism of imatinib in CML. Disclosures:No relevant conflicts of interest to declare.

Regulation of NF-κB-dependent Gene Expression by the POU Domain Transcription Factor Oct-1

Maintenance of the cells of the vessel wall in a quiescent state is an important aspect of normal vascular physiology. Transcriptional repressors are widely believed to regulate this process, yet the exact factors involved and the mechanism of repression are not known. Here, we report that the POU domain transcription factor Oct-1 represses the expression of E-selectin and vascular cell adhesion molecule (VCAM-1), two cytokine-inducible, NF-kappaB-dependent endothelial-leukocyte adhesion molecules that participate in the leukocyte recruitment phase of the inflammatory response. Co-transfection and microinjection studies demonstrate that Oct-1 blocks tumor necrosis factor alpha-stimulated E-selectin and VCAM-1 expression. Gene expression arrays indicate that control of tumor necrosis factor alpha-induced, NF-kappaB-dependent gene expression by Oct-1 is promoter-specific. A DNA-binding mutant of Oct-1 represses NF-kappaB-dependent reporter gene expression. Biochemically, Oct-1 interacts with p65, suggesting that Oct-1 is involved in the regulation of NF-kappaB transactivation function. NF-kappaB-dependent gene expression is more pronounced in Oct-1-deficient than in wild-type murine embryonic fibroblasts, and reintroduction of human Oct-1 abolishes these differences. Finally, the cytokine interleukin-6 induces Oct-1 gene expression, providing a biologically relevant means by which NF-kappaB-dependent gene expression can be selectively reverted by Oct-1 to quiescent levels.

An organic cation transporter capable of transporting serotonin is upregulated in serotonin transporter-deficient mice

The serotonin (5HT) transporter (5HTT) regulates serotonergic neurotransmission by mediating the reuptake of 5HT from the synaptic cleft. The organic cation transporter (OCT) gene family physiologically transports a wide spectrum of organic cations. Although lacking the high affinity and selectivity of the 5HTT, OCT1 and OCT3 mediate low-affinity 5HT transport and therefore may participate in the clearance of excessive 5HT. Since concentrations of extracellular 5HT are increased in the brain of 5HTT-deficient mice, we investigated the role of OCTs in 5HT system homeostasis. We analyzed OCT1 and OCT3 gene expression in the brain of 5HTT knockout mice by semi-quantitative competitive PCR and in situ hybridization. We demonstrate that in 5HTT-deficient mice OCT3 mRNA concentrations were significantly increased in the hippocampus. In contrast, OCT1 expression was unchanged. Upregulation of OCT3 expression and enhanced low-affinity 5HT uptake may limit the adverse effects of elevated extracellular 5HT and may play a critical role in maintaining 5HT-dependent functions of the hippocampus in the absence of 5HTT.

Regulation of oct-1 gene transcription is different in lymphoid and non-lymphoid cells

Transcription factor Oct-1 is expressed in all eukaryotic cells acting as a positive or negative regulator of gene transcription and DNA replication. Being a ubiquitous nuclear protein, Oct-1 also takes part in the regulation of tissue-specific gene expression. In this paper, we have found that human oct-1 gene is regulated by two promoters, located in OTF-1 locus upstream of 1U and 1L exons, respectively. The DNA region preceding U exon has a pattern typical of the constitutive gene promoters. The 5′-region upstream of 1L–exon is AT-rich, contains no TATA box, but has two octamer sequences targeted by Oct-1 and Oct-2 proteins. Analysis of promoter activity is carried out by transfection of recombinant plasmids in non-lymphoid HEK293 and lymphoid Raji cells. In non-lymphoid cells, efficiency of transcription from the 1U promoter several times exceeded that from the 1L promoter. The 1U promoter activity is little increased in the presence of an external enhancer. A different expression pattern was observed if the same constructs were transfected into lymphoid Raji cells. In this case, the level of transcription from the 1L promoter (the L–2 fragment, containing a proximal octamer site) in the presence of the enhancer was significantly higher than that of any fragments containing 1U promoter. It was shown that distal regions of both 1U and 1L were capable of silencing activity. In Raji cells, the enhancer completely overcomes the activity of U silencer, but only partly overcomes that of L silencer. Our data on tissue-specific features of 1L promoter and interaction of both oct-1 promoters with enhancer and silencers in different cell types point to a fine tissue-specific regulation of the oct-1 gene expression, especially in lymphoid cells.

Transcription Regulation of Human oct-1 Gene Requires Involvement of Two Promoters

Transcription initiation of human Oct-1 transcription factor-encoding gene involves two promoters, 1U and 1L, located at a substantial distance (about 100 kb) apart. The structure of these promoters and the adjacent sequences is different. Specifically, the 1U sequence is GC-rich, while the 1L sequence is AT-rich. Correspondingly, more than 25 GC-rich Sp1 cis-elements were localized within the 1U region, while in the 1L sequence nearly equal amount of homeo-specific NTAATNN sites along with two ATGCAAAT octamers were found. Analysis of transfection of recombinant plasmids, carrying the promoter fragments with or without enhancer indicated that expression from the 1L promoter was tissue-specific. In nonlymphoid HEK293 cells efficiency of transcription from the 1U promoter was several times higher than that from the 1L promoter. Another expression pattern was observed at transfection of the same constructs into Raji lymphoid cells. In this case the level of transcription from the L promoter (fragment L2) at the presence of external enhancer was higher than that from the fragments containing the 1U promoter. It was shown that the distal regions of 1U and 1L were capable of silencing activity. In Raji cells enhancer completely overcomes the activity of U silencer, but only partly overcomes the activity of L silencer. Our data on the interaction of two promoters with the enhancer and silencer in different cell types point to fine tissue-specific regulation of the oct-1 gene expression, especially in lymphatic cells.

Organic cation transporter capable of transporting serotonin is up-regulated in serotonin transporter-deficient mice.

The serotonin (5HT) transporter (5HTT) regulates serotonergic neurotransmission by mediating the reuptake of 5HT from the synaptic cleft. Although lacking the high affinity and selectivity of the 5HTT, the brain expresses a large number of other transporters, including the polyspecific organic cation transporters (OCTs). OCT1 and OCT3, members of the potential-sensitive organic cation transporter gene family, physiologically transport a wide spectrum of organic cations. In addition, both transporters mediate low-affinity 5HT transport and, therefore, may participate in the clearance of excessive 5HT. Because concentrations of extracellular 5HT are increased in the brain of 5HTT-deficient mice, they are a model for investigating the role of OCTs in 5HT system homeostasis. Here, we analyzed OCT1 and OCT3 gene expression in the brain of 5HTT knockout mice by semiquantitative competitive polymerase chain reaction and in situ hybridization. We demonstrate that, in 5HTT-deficient mice, OCT3 mRNA concentrations were significantly increased in the hippocampus, but not in other brain regions, including cortex, striatum, cerebellum, and brainstem. In contrast, no difference in OCT1 expression was detected between 5HTT knockout and control mice. Up-regulation of OCT3 expression and enhanced low-affinity 5HT uptake may limit the adverse effects of elevated extracellular 5HT and may play a critical role in maintaining 5HT-dependent functions of the hippocampus in the absence of 5HTT.

Tissue-specific isoforms of the ubiquitous transcription factor Oct-1.

The ubiquitously expressed transcription factor Oct-1 is a member of the POU protein family. It is involved in the activation of snRNA promoters and some mRNA promoters (e.g., promoters and enhancers of genes for histone H2B and immunoglobulins). In this work we have cloned and sequenced a new Oct-1 isoform, named Oct-1L. Both Oct-1L mRNA and Oct-1R mRNA (cloned earlier) are expressed in lymphocytes, but not in any other cell line tested. This is the first report of tissue-specific Oct-1 gene expression. Both these forms differ from the ubiquitously expressed Oct-1 isoforms in the N-termini. They are probably generated by alternative splicing and/or alternative initiation of transcription. The latter is confirmed by the localization of transcription start points upstream of exons 1L (lymphocyte-specific) and IU (ubiquitously expressed). We assume that tissue-specific expression of Oct-1L and Oct-1R in lymphocytes and their structural differences from the ubiquitously expressed Oct-1 isoforms may be related to B and T cell differentiation and/or expression of the immunoglobulin genes.

Oct-1 promoter region contains octamer sites and TAAT motifs recognized by Oct proteins

The 5′-upstream region (1.3 kb) of the gene encoding the POU domain transcription factor Oct-1 was cloned and sequenced. CAT reporter gene analysis of this region has detected a functionally active promoter. This region contains 24 TAAT-core sites, arranged in five clusters (four to six sites in one cluster); two octamer sites (ATGCAAAT) are located in the first and second clusters; in the second one the CCAAT-box adjacent to the octamer overlaps with the TAAT-core site. As shown by gel retardation assay, Oct-1, Oct-2, and some unknown proteins from myeloma cell line NS/0 interact with the TAAT-core sites of these clusters. The results suggest autoregulation of Oct-1 gene expression that may also be controlled by other POU proteins, homeodomain proteins and CCAAT trans-action factors.

Perlecan regulates Oct-1 gene expression in vascular smooth muscle cells.

Vascular smooth muscle cells (SMCs) are very quiescent in the mature vessel and exhibit a remarkable phenotype-dependent diversity in gene expression that may reflect the growth responsiveness of these cells under a variety of normal and pathological conditions. In this report, we describe the expression pattern of Oct-1, a member of a family of transcription factors involved in cell growth processes, in cultured and in in vivo SMCs. Oct-1 mRNA was undetectable in the contractile-state in vivo SMCs; was induced upon disruption of in vivo SMC-extracellular matrix interactions; and was constitutively expressed by cultured SMCs. Oct-1 transcripts were repressed when cultured SMCs were plated on Engelbreth-Holm-Swarm tumor-derived basement membranes (EHS-BM) but were rapidly induced after disruption of SMC-EHS-BM contacts; reexpression was regulated at the transcriptional level. To identify the EHS-BM component involved in the active repression of Oct-1 mRNA expression, SMCs were plated on laminin, type IV collagen, fibronectin, or perlecan matrices. Oct-1 mRNA levels were readily detectable when SMCs were cultured on matrices composed of laminin, type IV collagen, or fibronectin but were repressed when SMCs were cultured on perlecan matrices. Finally, the Oct-1-suppressing activity of EHS-BM was sensitive to heparinase digestion but not to chondroitinase ABC or hyaluronidase digestion, suggesting that the heparan sulfate side chains of perlecan play a biologically important role in negatively regulating the expression of Oct-1 transcripts.