Identification of the Transcription Factors of CD200R1 and Its Potential Roles in Parkinson’s Disease

BackgroundNeuroinflammation is known to be involved in the pathogenesis of Parkinson's disease (PD). Abnormal activation of microglia plays a key role in this pathological process. CD200R1 is a membrane glycoprotein primarily expressed in microglia in central nervous system responsible for transducing signaling maintaining microglia in stationary status. Our previous studies have demonstrated the dysregulation of CD200R1 and its involvement in PD pathogenesis. The binding of transcription factors with promoter regions is the basic and essential step for the regulation of gene expression. However, little is known about the human CD200R1 promoter region and the mechanism of the dysregulated expression of CD200R1 in PD. MethodsLuciferase reporter system was initially employed to identify the core region of CD200R1 promoter and figure out its potential transcription factors. Subsequently, we investigated the interaction adopting electrophoretic mobility shift assay and chromatin immunoprecipitation assay. The regulatory function of the detected transcription factors were further proved through its down-regulation and overexpression. We then collected the peripheral blood mononuclear cells from both PD patients and their healthy counterparts with matched age and sex to evaluate whether consistent results existed under clinical setting. Ultimately, the mouse model was established through knocking-out the identified transcription factor and its role in neuroinflammation and pathogenesis of PD was explored. ResultsWe defined that the core promoter region of CD200R was located within -482 to -146 bp upstream of the translation initiation site (TIS). In addition, we demonstrated that NFKB1 directly bound to the CD200R1 core promoter region and regulated its transcriptional activity. Besides, the expression of NFKB1 and CD200R1 was significantly correlated in human peripheral blood mononuclear cells and knocking down NFKB1 significantly reduced CD200R1 expression. Moreover, both NFKB1 and CD200R1 were significantly downregulated in samples from PD patients. Furthermore, NFKB1-/- mice exhibited exacerbated microglia activation and dopaminergic neuron loss after MPTP treatment. ConclusionOur study provided novel understanding of the transcriptional regulation of CD200R1 and its role in microglia homeostasis in the pathogenesis of PD.

The Core Promoter Is a Regulatory Hub for Developmental Gene Expression

The development of multicellular organisms and the uniqueness of each cell are achieved by distinct transcriptional programs. Multiple processes that regulate gene expression converge at the core promoter region, an 80 bp region that directs accurate transcription initiation by RNA polymerase II (Pol II). In recent years, it has become apparent that the core promoter region is not a passive DNA component, but rather an active regulatory module of transcriptional programs. Distinct core promoter compositions were demonstrated to result in different transcriptional outputs. In this mini-review, we focus on the role of the core promoter, particularly its downstream region, as the regulatory hub for developmental genes. The downstream core promoter element (DPE) was implicated in the control of evolutionarily conserved developmental gene regulatory networks (GRNs) governing body plan in both the anterior-posterior and dorsal-ventral axes. Notably, the composition of the basal transcription machinery is not universal, but rather promoter-dependent, highlighting the importance of specialized transcription complexes and their core promoter target sequences as key hubs that drive embryonic development, differentiation and morphogenesis across metazoan species. The extent of transcriptional activation by a specific enhancer is dependent on its compatibility with the relevant core promoter. The core promoter content also regulates transcription burst size. Overall, while for many years it was thought that the specificity of gene expression is primarily determined by enhancers, it is now clear that the core promoter region comprises an important regulatory module in the intricate networks of developmental gene expression.

A combinatorial cis-regulatory logic restricts color-sensing Rhodopsins to specific photoreceptor subsets in Drosophila

Color vision in Drosophila melanogaster is based on the expression of five different color-sensing Rhodopsin proteins in distinct subtypes of photoreceptor neurons. Promoter regions of less than 300 base pairs are sufficient to reproduce the unique, photoreceptor subtype-specific rhodopsin expression patterns. The underlying cis-regulatory logic remains poorly understood, but it has been proposed that the rhodopsin promoters have a bipartite structure: the distal promoter region directs the highly restricted expression in a specific photoreceptor subtype, while the proximal core promoter region provides general activation in all photoreceptors. Here, we investigate whether the rhodopsin promoters exhibit a strict specialization of their distal (subtype specificity) and proximal (general activation) promoter regions, or if both promoter regions contribute to generating the photoreceptor subtype-specific expression pattern. To distinguish between these two models, we analyze the expression patterns of a set of hybrid promoters that combine the distal promoter region of one rhodopsin with the proximal core promoter region of another rhodopsin. We find that the function of the proximal core promoter regions extends beyond providing general activation: these regions play a previously underappreciated role in generating the non-overlapping expression patterns of the different rhodopsins. Therefore, cis-regulatory motifs in both the distal and the proximal core promoter regions recruit transcription factors that generate the unique rhodopsin patterns in a combinatorial manner. We compare this combinatorial regulatory logic to the regulatory logic of olfactory receptor genes and discuss potential implications for the evolution of rhodopsins.

Identification and characterization of a G-quadruplex structure in the pre-core promoter region of hepatitis B virus

ABSTRACTWorldwide, ∼250 million people are chronically infected with the hepatitis B virus (HBV) and are at increased risk of cirrhosis and hepatocellular carcinoma. The HBV persists as covalently closed circular DNA (cccDNA), which acts as the template for all HBV mRNA transcripts. Nucleos(t)ide analogs do not directly target the HBV cccDNA and cannot eradicate the HBV. We have discovered a unique structural motif, a G-quadruplex in HBV’s pre-core promoter region that is conserved amongst nearly all genotypes, and is central to critical steps in the viral life-cycle including the production of pre-genomic RNA, core and polymerase proteins, and encapsidation. Thus, an increased understanding of the HBV pre-core may lead to the development of novel anti-HBV cccDNA targets. We utilized biophysical methods to characterize the presence of the G-quadruplex, employed assays using a known quadruplex-binding protein (DHX36) to pull-down HBV cccDNA, and compared HBV infection in HepG2 cells transfected with wild-type and mutant HBV plasmids. This study provides insights into the presence of a G-quadruplex in the HBV pre-core promoter region essential for HBV replication. The evaluation of this critical host-protein interaction site in the HBV cccDNA may ultimately facilitate the development of novel anti-HBV therapeutics against the resilient cccDNA template.

35 Characterization of the promoter region of ZNFO, an oocyte-specific gene in cattle

Maternal factors are essential aspects of oocyte competence, which orchestrate early embryonic development. ZNFO is a Krüppel-associated box domain (KRAB) containing zinc finger transcription factor, which is exclusively expressed in bovine oocyte. Previous studies have demonstrated that ZNFO is essential for early embryonic development. However, the mechanisms regulating ZNFO transcription remain elusive. The objective of present study is to elucidate regulatory mechanisms of ZNFO transcription invitro, and specifically to identify putative core promoter and transcription factor(s) regulating ZNFO expression. 5′ Random amplification of cDNA ends (RACE) was performed using RNA isolated from 100 germinal vesicle (GV) stage oocytes to identify the transcription start site (TSS) of ZNFO. To elucidate the molecular mechanisms of ZNFO transcription, a 1.7-kb fragment of the 5′ regulatory region was obtained and cloned into pGL4.14 promoterless vector. The luciferase reporter assay was performed to confirm the promoter activity of the regulatory region. To further identify the core promoter region of the putative ZNFO promoter, a series of 5′ deletions in the ZNFO promoter followed by luciferase reporter assay was performed. The luciferase results indicated that the core promoter region of ZNFO was located within a region 57 to 31bp upstream of the transcription start site. Bioinformatics analysis indicated that a putative USF1/USF2 binding site (GGTCTCGTGACC) is located within the core promoter region. USF1 is a basic helix–loop–helix leucine zipper transcription factor, which regulates the expression of various maternal genes, which are essential for oocyte maturation and early embryonic development in cattle. To confirm that USF1 regulated ZNFO expression, bovine USF1 open reading frame (ORF) was cloned into pcDNA3.1A-HA vector, generating a USF1 overexpression construct. Overexpression of USF1 by transfecting USF1 plasmid enhanced ZNFO promoter activity within HEK293 cells, confirming that ZNFO expression is regulated by USF1. From these results, we conclude that USF1 activates the ZNFO promoter by binding to its target site, GGTCTCGTGACC.

Compartmentalized evolution of hepatitis B virus contributes differently to the prognosis of hepatocellular carcinoma

Serum hepatitis B virus (HBV) mutations can predict hepatocellular carcinoma (HCC) occurrence. We aimed to clarify if HBV evolves synchronously in the sera, adjacent liver, and tumors and predict HCC prognosis equally. A total of 203 HBV-positive HCC patients with radical hepatectomy in Shanghai, China during 2011-2015 were enrolled in this prospective study. Quasispecies complexity (QC) in HBV core promoter region was assessed using clone-based sequencing. We performed RNA-sequencing on tumors and paired adjacent tissues of another 15 HCC patients and analyzed it with 3 public datasets containing 127 samples. HBV QC was positively correlated to APOBEC3s’ expression level (r=0.28, p<0.001), higher in the adjacent tissues than in the tumors (p=6.50e-3), and higher in early tumors than in advanced tumors (p=0.039). The evolutionary distance between the sera-derived HBV strains and the tumor-derived ones was significantly longer than that between the sera-derived ones and the adjacent tissue-derived ones (p<0.001). Multivariate Cox regression analyses indicated that high HBV QC in the sera predicted an unfavorable overall survival (OS) (p=0.002) and recurrence-free survival (RFS) (p=0.004) in HCC; whereas it in the tumors predicted a favorable RFS (p<0.001), respectively. APOBECs-related HBV mutations including G1764A were more frequent in the sera than in the adjacent tissues. High-frequent A1762T/G1764A in the sera predicted an unfavorable RFS (p<0.001); whereas it in the tumors predicted a favorable RFS (p=0.035). In conclusion, HBV evolves more advanced in the sera than in the tumors. HBV QC and A1762T/G1764A in the sera and tumors have contrary prognostic effects in HCC.

Transcriptional Regulation of HMOX1 Gene in Hezuo Tibetan Pigs: Roles of WT1, Sp1, and C/EBPα

Heme oxygenase 1 (HMOX1) is a stress-inducing enzyme with multiple cardiovascular protective functions, especially in hypoxia stress. However, transcriptional regulation of swine HMOX1 gene remains unclear. In the present study, we first detected tissue expression profiles of HMOX1 gene in adult Hezuo Tibetan pig and analyzed the gene structure. We found that the expression level of HMOX1 gene was highest in the spleen of the Hezuo Tibetan pig, followed by liver, lung, and kidney. A series of 5’ deletion promoter plasmids in pGL3-basic vector were used to identify the core promoter region and confirmed that the minimum core promoter region of swine HMOX1 gene was located at −387 bp to −158 bp region. Then we used bioinformatics analysis to predict transcription factors in this region. Combined with site-directed mutagenesis and RNA interference assays, it was demonstrated that the three transcription factors WT1, Sp1 and C/EBPα were important transcription regulators of HMOX1 gene. In summary, our study may lay the groundwork for further functional study of HMOX1 gene.

The Molecular Characteristics of the FAM13A Gene and the Role of Transcription Factors ACSL1 and ASCL2 in Its Core Promoter Region

The gene family with sequence similarity 13 member A (FAM13A) has recently been identified as a marker gene in insulin sensitivity and lipolysis. In this study, we first analyzed the expression patterns of this gene in different tissues of adult cattle and then constructed a phylogenetic tree based on the FAM13A amino acid sequence. This showed that subcutaneous adipose tissue had the highest expression in all tissues except lung tissue. Then we summarized the gene structure. The promoter region sequence of the gene was successfully amplified, and the −241/+54 region has been identified as the core promoter region. The core promoter region was determined by the unidirectional deletion of the 5’ flanking promoter region of the FAM13A gene. Based on the bioinformatics analysis, we examined the dual luciferase activity of the vector constructed by the mutation site, and the transcription factors ACSL1 and ASCL2 were found as transcriptional regulators of FAM13A. Moreover, electrophoretic mobility shift assay (EMSA) further validated the regulatory role of ACSL1 and ASCL2 in the regulation of FAM13A. ACSL1 and ASCL2 were finally identified as activating transcription factors. Our results provide a basis for the function of the FAM13A gene in bovine adipocytes in order to improve the deposition of fat deposition in beef cattle muscle.

High Frequency of Either Altered Pre-Core Start Codon or Weakened Kozak Sequence in the Core Promoter Region in Hepatitis B Virus A1 Strains from Rwanda

Hepatitis B virus (HBV) is endemic in Rwanda and is a major etiologic agent for chronic liver disease in the country. In a previous analysis of HBV strains from Rwanda, the S genes of most strains segregated into one single clade of subgenotype, A1. More than half (55%) of the anti-HBe positive individuals were viremic. In this study, 23 complete HBV genomes and the core promoter region (CP) from 18 additional strains were sequenced. Phylogenetic analysis of complete genomes confirmed that most Rwandan strain formed a single unique clade, within subgenotype A1. Strains from 17 of 22 (77%) anti-HBe positive HBV carriers had either mutated the precore start codon (9 strains with either CUG, ACG, UUG, or AAG) or mutations in the Kozak sequence preceding the pre-core start codon (8 strains). These mutually exclusive mutations were also identified in subgenotypes A1 (70/266; 26%), A2 (12/255; 5%), and A3 (26/49; 53%) sequences from the GenBank. The results showed that previous, rarely described HBV variants, expressing little or no HBeAg, are selected in anti-HBe positive subgenotype Al carriers from Rwanda and that mutations reducing HBeAg synthesis might be unique for a particular HBV clade, not just for a specific genotype or subgenotype.