Selective modulation of the SM22alpha promoter by the binding of BTEB3 (basal transcription element-binding protein 3) to TGGG repeats

KLF13 promotes VSMCs phenotypic dedifferentiation by directly binding to the SM22α promoter

Krüppel-like factor 13 (KLF13), a zinc finger transcription factor, is considered as a potential regulator of cardiomyocyte differentiation and proliferation during heart morphogenesis. However, its precise role in the dedifferentiation of vascular smooth muscle cells (VSMCs) during atherosclerosis and neointimal formation after injury remains poorly understood. In this study, we investigated the relationship between KLF13 and SM22α expression in normal and atherosclerotic plaques by bioanalysis, and observed a significant increase in KLF13 levels in the atherosclerotic plaques of both human patients and ApoE-/- mice. Knockdown of KLF13 was found to ameliorate intimal hyperplasia following carotid artery injury. Furthermore, we discovered that KLF13 directly binds to the SM22α promoter, leading to the phenotypic dedifferentiation of VSMCs. Remarkably, we observed a significant inhibition of platelet-derived growth factor BB-induced VSMCs dedifferentiation, proliferation, and migration when knocked down KLF13 in VSMCs. This inhibitory effect of KLF13 knockdown on VCMC function was, at least in part, mediated by the inactivation of p-AKT signaling in VSMCs. Overall, our findings shed light on a potential therapeutic target for treating atherosclerotic lesions and restenosis after vascular injury.

Krüppel-like Factor-9 and Krüppel-like Factor-13: Highly Related, Multi-Functional, Transcriptional Repressors and Activators of Oncogenesis

Specificity Proteins/Krüppel-like Factors (SP/KLF family) are a conserved family of transcriptional regulators. These proteins share three highly conserved, contiguous zinc fingers in their carboxy-terminus, requisite for binding to cis elements in DNA. Each SP/KLF protein has unique primary sequence within its amino-terminal and carboxy-terminal regions, and it is these regions which interact with co-activators, co-repressors, and chromatin-modifying proteins to support the transcriptional activation and repression of target genes. Krüppel-like Factor 9 (KLF9) and Krüppel-like Factor 13 (KLF13) are two of the smallest members of the SP/KLF family, are paralogous, emerged early in metazoan evolution, and are highly conserved. Paradoxically, while most similar in primary sequence, KLF9 and KLF13 display many distinct roles in target cells. In this article, we summarize the work that has identified the roles of KLF9 (and to a lesser degree KLF13) in tumor suppression or promotion via unique effects on differentiation, pro- and anti-inflammatory pathways, oxidative stress, and tumor immune cell infiltration. We also highlight the great diversity of miRNAs, lncRNAs, and circular RNAs which provide mechanisms for the ubiquitous tumor-specific suppression of KLF9 mRNA and protein. Elucidation of KLF9 and KLF13 in cancer biology is likely to provide new inroads to the understanding of oncogenesis and its prevention and treatments.

Bioinformatic identification of candidate genes induced by trichostatin A in BGC-823 gastric cancer cells

The aim of the present study was to identify the candidate genes induced by trichostatin A (TSA) in BGC-823 gastric cancer (GC) cells and to explore the possible inhibition mechanism of TSA in GC. Gene expression data were obtained through chip detection, and differentially expressed genes (DEGs) between GC cells treated with TSA and untreated GC cells (control group) were identified. Gene ontology analysis of the DEGs was performed using the database for annotation, visualization and integrated discovery. Then sub-pathway enrichment analysis was performed and a microRNA (miRNA) regulatory network was constructed. We selected 76 DEGs, among which 43 were downregulated genes and 33 were upregulated genes. By sub-pathway enrichment analysis of the DEGs, the propanoate metabolism pathway was selected as the sub-pathway. By constructing a miRNA regulatory network, we identified that DKK1 and KLF13 were the top hub nodes. The propanoate metabolism pathway and the genes DKK1 and KLF13 may play significant roles in the inhibition of GC induced by TSA. These genes may be potential therapeutic targets for GC. However, further experiments are still required to confirm our results.

A C2H2 zinc finger protein FEMU2 is required for fox1 expression in Chlamydomonas reinhardtii

Chlamydomonas reinhardtii fox1 gene encodes a ferroxidase that is involved in cellular Fe uptake and highly induced during Fe deficient conditions. In an effort to identify fox1 promoter regulatory elements, an insertional library was generated in a transgenic Chlamydomonas strain (2A38) harboring an arylsulfatase (ARS) reporter gene driven by the fox1 promoter. Mutants with a defective response to low iron conditions were selected for further study. Among these, a strain containing a disrupted femu2 gene was identified. Activation of the fox1 promoter by the femu2 gene product was confirmed by silencing the femu2 gene using RNA interference. In three femu2 RNAi transgenic lines (IR3, IR6, and IR7), ARS reporter gene activities declined by 84.3%, 86.4%, and 88.8%, respectively under Fe deficient conditions. Furthermore, RT-PCR analysis of both the femu2 mutant and the RNAi transgenic lines showed significantly decreased transcript abundance of the endogenous fox1 gene under Fe deficient conditions. Amino acid sequence analysis of the femu2 gene product identified three potential C2H2 zinc finger (ZF) motifs and a nuclear localization study suggests that FEMU2 is localized to the nucleus. In addition, a potential FEMU2 binding site ((G/T)TTGG(G/T)(G/T)T) was identified using PCR-mediated random binding site selection. Taken together, this evidence suggests that FEMU2 is involved in up-regulation of the fox1 gene in Fe deficient cells.

Overexpression of KLF13 and FGFR3 in oral cancer cells

KLF13 and FGFR3 have important cellular functions and each is believed to play a role in cancer. KLF13 is a transcription factor required for the expression of several oncogenes. FGFR3 is a fibroblast growth factor receptor that initiates a signaling cascade leading to the activation of numerous cellular pathways. Here we show that KLF13 and FGFR3 are overexpressed in oral cancer cells. We also show that artificially reducing cellular levels of KLF13 and FGFR3 decreases cell proliferation and increases sensitivity to ionizing radiation. These data suggest that KLF13 and FGFR3 contribute to malignancy in oral cancer cells and may be useful biomarkers for early detection and possible targets for therapy.

Kruppel-like Factors (KLFs) in muscle biology

The Kruppel-like Factor (KLF) family of zinc-finger transcription factors are critical regulators of cell differentiation, phenotypic modulation and physiologic function. An emerging body of evidence implicates an important role for these factors in cardiovascular biology, however, the role of KLFs in muscle biology is only beginning to be understood. This article reviews the published data describing the role of KLFs in the heart, smooth muscle, and skeletal muscle and highlights the importance of these factors in cardiovascular development, physiology and disease pathobiology.

The Kruppel-like transcription factor KLF13 is a novel regulator of heart development

In humans, congenital heart defects occur in 1-2% of live birth, but the molecular mechanisms and causative genes remain unidentified in the majority of cases. We have uncovered a novel transcription pathway important for heart morphogenesis. We report that KLF13, a member of the Krüppel-like family of zinc-finger proteins, is expressed predominantly in the heart, binds evolutionarily conserved regulatory elements on cardiac promoters and activates cardiac transcription. KLF13 is conserved across species and knockdown of KLF13 in Xenopus embryos leads to atrial septal defects and hypotrabeculation similar to those observed in humans or mice with hypomorphic GATA-4 alleles. Physical and functional interaction with GATA-4, a dosage-sensitive cardiac regulator, provides a mechanistic explanation for KLF13 action in the heart. The data demonstrate that KLF13 is an important component of the transcription network required for heart development and suggest that KLF13 is a GATA-4 modifier; by analogy to other GATA-4 collaborators, mutations in KLF13 may be causative for congenital human heart disease.

An emerging role for Krüppel-like factors in vascular biology

The Krüppel-like family of transcription factors play diverse roles regulating cellular differentiation and tissue development. Accumulating evidence supports an important role for these factors in vascular biology. This review examines the current knowledge of this gene family's role in key cell types that critically regulate vessel biology under physiologic and pathologic states.