Project description:Alu SINEs are the most numerous frequently occurring transcription units in our genome and possess sequence competence for transcription by RNA Pol III. However, through poorly understood mechanisms, the Alu RNA levels are maintained at very low levels in normal somatic cells with obvious benefits of low rates of Alu retrotransposition and energy-economical deployment of RNA Pol III to the tRNA genes which share promoter structure and polymerase requirements with Alu SINEs. Using comparative ChIP sequencing, we unveil that a repeat binding protein, CGGBP1, binds to the transcriptional regulatory regions of Alu SINEs thereby impeding Alu transcription by inhibiting RNA Pol III recruitment. We show that this Alu-silencing depends on growth factor stimulation of cells and subsequent tyrosine phosphorylation of CGGBP1. Importantly, CGGBP1 ensures a sequence-specific discriminative inhibition of RNA Pol III activity at Alu promoters, while sparing the structurally similar tRNA promoters. Our data suggest that CGGBP1 contributes to growth-related transcription by preventing the hijacking of RNA Pol III by Alu SINEs. This study was used to find out the effect of CGGBP1 on serum-induced changes in gene expression and effect of serum on gene expression regulation by CGGBP1. Gene expression profiling of normal human fibroblasts under 4 different experimental perturbations: serum starvation or serum stimulation and CGGBP1 depletion or normal CGGBP1 levels.
Project description:Alu SINEs are the most numerous frequently occurring transcription units in our genomes and possess sequence competence for transcription by RNA Pol III. However, through poorly understood mechanisms, the Alu RNA levels are maintained at very low levels in normal somatic cells with obvious benefits of low rates of Alu retrotransposition and energy-economical deployment of RNA Pol III to the tRNA genes which share promoter structure and polymerase requirements with Alu SINEs. Using comparative ChIP sequencing, we unveil that a repeat binding protein, CGGBP1, binds to the transcriptional regulatory regions of Alu SINEs thereby impeding Alu transcription by inhibiting RNA Pol III recruitment. We show that this Alu-silencing depends on growth factor stimulation of cells and subsequent tyrosine phosphorylation of CGGBP1. Importantly, CGGBP1 ensures a sequence-specific discriminative inhibition of RNA Pol III activity at Alu promoters, while sparing the structurally similar tRNA promoters. Our data suggest that CGGBP1 contributes to growth-related transcription by preventing the hijacking of RNA Pol III by Alu SINEs. Examination of one DNA binding protein in two different conditions of treatment.
Project description:Alu SINEs are the most numerous frequently occurring transcription units in our genomes and possess sequence competence for transcription by RNA Pol III. However, through poorly understood mechanisms, the Alu RNA levels are maintained at very low levels in normal somatic cells with obvious benefits of low rates of Alu retrotransposition and energy-economical deployment of RNA Pol III to the tRNA genes which share promoter structure and polymerase requirements with Alu SINEs. Using comparative ChIP sequencing, we unveil that a repeat binding protein, CGGBP1, binds to the transcriptional regulatory regions of Alu SINEs thereby impeding Alu transcription by inhibiting RNA Pol III recruitment. We show that this Alu-silencing depends on growth factor stimulation of cells and subsequent tyrosine phosphorylation of CGGBP1. Importantly, CGGBP1 ensures a sequence-specific discriminative inhibition of RNA Pol III activity at Alu promoters, while sparing the structurally similar tRNA promoters. Our data suggest that CGGBP1 contributes to growth-related transcription by preventing the hijacking of RNA Pol III by Alu SINEs.
Project description:Alu SINEs are the most numerous frequently occurring transcription units in our genome and possess sequence competence for transcription by RNA Pol III. However, through poorly understood mechanisms, the Alu RNA levels are maintained at very low levels in normal somatic cells with obvious benefits of low rates of Alu retrotransposition and energy-economical deployment of RNA Pol III to the tRNA genes which share promoter structure and polymerase requirements with Alu SINEs. Using comparative ChIP sequencing, we unveil that a repeat binding protein, CGGBP1, binds to the transcriptional regulatory regions of Alu SINEs thereby impeding Alu transcription by inhibiting RNA Pol III recruitment. We show that this Alu-silencing depends on growth factor stimulation of cells and subsequent tyrosine phosphorylation of CGGBP1. Importantly, CGGBP1 ensures a sequence-specific discriminative inhibition of RNA Pol III activity at Alu promoters, while sparing the structurally similar tRNA promoters. Our data suggest that CGGBP1 contributes to growth-related transcription by preventing the hijacking of RNA Pol III by Alu SINEs. This study was used to find out the effect of CGGBP1 on serum-induced changes in gene expression and effect of serum on gene expression regulation by CGGBP1.
Project description:Nearly half the human genome is comprised of repetitive DNA, including short interspersed nuclear elements (SINEs) such as Alu. SINEs spread by retrotransposition, which requires their transcripts to be copied into DNA and then inserted into new chromosomal sites. This can lead to genetic damage through insertional mutagenesis and through chromosomal rearrangements between nonallelic SINEs at distinct loci. SINE DNA is heavily methylated and this is thought to suppress its accessibility and transcription, thereby protecting against retrotransposition. However, we provide several lines of evidence that methylated SINE DNA is occupied genome-wide by RNA polymerase III, including the use of high-throughput bisulphite sequencing of ChIP DNA (ChIP-BS-Seq). Loss of DNA methylation has little effect on expression of SINEs or their accessibility to transcription machinery. We present evidence that methylation of histones rather than DNA plays a dominant role in suppressing SINE expression.
Project description:By depleting CGGBP1 in normal human fibroblasts and by performing genome-wide sequencing (with and without bisulfite conversion) we show that upon CGGBP1 depletion cytosine methylation increases significantly at repeat regions. Using Pacbio sequencing of Alu and LINE-1 repeats amplified genome-wide from bisulfite converted DNA, we further establish the cytosine methylation-inhibitory functions of CGGBP1.
Project description:CGGBP1-dependent CTCF-binding sites identified in Patel et. al. 2019 [PMID 31547883] serve as barrier elements consistent with asymmetrical levels of H3K9me3 in the flanks and asymmetrical RNA levels at these sites in the genome. In this study we have characterised the function of such CGGBP1-depenedent CTCF binding sites which are usually repeat rich in nature. By cloning one such CTCF-binding site in an episomal system, we have studied the barrier activity of this CGGBP1-dependent CTCF-binding sites in the prsesnce and absence of CGGBP1 in HEK293T cells through various molecular assays and RNA-sequencing. Our results show that these sites act as barrier for the ectopic transcription as the depletion of CGGBP1 lead to starnd-specific bidirectional transcription as a result of loss of barrier activity concomitant with the loss of CTCF-binding. Further, analysing the RNA-seq revealed that weakly transcribed sites are flanked by the CTCF-binding at transcription start and end sites in the presence of CGGBP1. However, CGGBP1 depletion leads to loss of barrier activity maintained by CGGBP1 with dispersed CTCF binding and a loss of transcription restriction. Such CGGBP1-dependent CTCF-binding sites prevents ectopic transcription.
Project description:Truncated forms of CGGBP1 with (N-term) or without (C-term) the DNA-binding domain (DBD) have been used to to assay global gene expression. HEK293T cells with endogenous CGGBP1 knocked down were used to over-express truncated forms of CGGBP1 followed by RNA extraction and one-coloured global gene expression analysis. The data suggests that while the C-term of CGGBP1 is the major repressor of transcription, just the N-term containing the DBD fails to achieve so. Proximal promoters of CGGBP1-repressed genes, although significantly GC-poor, contain GC-rich transcription factor binding motifs and exhibit base compositions indicative of low C-T transition rates due to targeted prevention of cytosine methylation. Our findings suggest that CGGBP1 protects transcription factor binding sites (TFBS) from cytosine methylation-associated loss and thereby regulates gene expression. By analysing orthologous promoter sequences, we show that protection from cytosine methylation is a function of CGGBP1 progressively acquired during vertebrate evolution.