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:Human CGGBP1 has been attributed multiple function related to the regulation of gene expression, cytosine methylation (including non-CpG methylation), related epigenetic states of target gene promoter regions and somatic mutation rates. CGGBP1 has also been shown to be a prominent transcription repressor of protein coding genes as well as repetitive elements, mainly Alu-SINEs. There is a possibility that CGGBP1-regulated cytosine methylation affects base mutation rates (C-T transitions) thereby directing TFBS evolution in the human genome. Some recent data suggest that the DNA-binding activity of human CGGBP1 prevents TFBS from cytosine methylation and preserves their GC content. The DNA-binding domain of CGGBP1 is conserved more than its other segments which contain no identifiable domains. In this study we assay global cytosine methylation using MeDIP-seq on human cells (HEK293T) over-expressing only representative vertebrate species (Latimeria chalumnae (Lc), Anolis carolinenesis (Ac), Gallus gallus (Gg), Homo sapiens (Hs)) and perform comparative analyses. Our analyses encompass a parallel global expression profiling (using Agilent arrays, submitted separately to NCBI GEO) and a large-scale estimation of TFBS C-T transition mutation rates from orthologs of genes repressed by the various forms of CGGBP1 used in this study. We report that cytosine methylation restriction by CGGBP1 promotes GC retention in some GC-rich TFBSs.
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:Short tracts of trinucleotide repeats with less than 10 repeats are found frequently throughout the genome without any apparent negative impact on DNA replication fork progression or transcription elongation. CGG binding protein 1 (CGGBP1) binds to CGG triplet repeats and has been implicated in multiple cellular processes such as transcription, replication and DNA damage. Here, we show that CGGBP1 binds to human gene promoter sites with short CGG repeat tracts prone to G-quadruplex and R-loop secondary structure formation. Depletion of CGGBP1 in human cells leads to substantial transcriptomic changes which coincides with increased replication fork stalling and transcription-replication conflicts. Consistently, an episomal model locus as well as endogenous candidate genes containing short tracts of CGG repeats show R-loop accumulation and increased RNAPII chromatin occupancy in CGGBP1-depleted cells. Mass spectrometry identifies the DEAD-box helicase DDX41 as a specific interaction partner of CGGBP1, thereby providing mechanistic insight how CGGBP1 can counteract the formation of secondary DNA structures at CGG repeats. Together, our work shows that short trinucleotide repeats are a source of genome-destabilizing secondary structures and cells rely on specific DNA-binding factors to maintain proper transcription and replication progression at short trinucleotide repeats.