A Unifying Model for Molecular Determinants of the Pre-selection V Repertoire
ABSTRACT: Analysis of histone modifications in double negative thymocytes from RAG-/- mice For the ChIP-seq, input and immunoprecipitated DNA was given to The Scripps DNA Array Facility, where it was prepared for massively parallel sequencing on Illumina HiSeq 2000.
Proceedings of the National Academy of Sciences of the United States of America 20130805 34
The primary antigen receptor repertoire is sculpted by the process of V(D)J recombination, which must strike a balance between diversification and favoring gene segments with specialized functions. The precise determinants of how often gene segments are chosen to complete variable region coding exons remain elusive. We quantified Vβ use in the preselection Tcrb repertoire and report relative contributions of 13 distinct features that may shape their recombination efficiencies, including transcri ...[more]
Project description:A diverse antibody repertoire is formed through the rearrangement of V, D, and J segments at the immunoglobulin heavy chain (Igh) loci. The C57BL/6 murine Igh locus has over 100 functional VH gene segments that can recombine to a rearranged DJH. While the non-random usage of VH genes is well documented, it is not clear what elements determine recombination frequency. To answer this question we conducted deep sequencing of 5’-RACE products of the Igh repertoire in pro-B cells, amplified in an unbiased manner. ChIP-seq results for several histone modifications and RNA polymerase II binding, RNA-seq for sense and antisense non-coding germline transcripts, and proximity to CTCF and Rad21 sites were compared to the usage of individual V genes. Computational analyses assessed the relative importance of these various accessibility elements. These elements divide the Igh locus into four epigenetically and transcriptionally distinct domains, and our computational analyses reveal different regulatory mechanisms for each region. Proximal V genes are relatively devoid of active histone marks and non-coding RNA in general, but having a CTCF site near their RSS is critical, suggesting that position near the base of the chromatin loops is important for rearrangement. In contrast, distal V genes have high levels of histone marks and non-coding RNA, which may compensate for their poorer RSS and for being distant from CTCF sites. Thus, the Igh locus has evolved a complex system for the regulation of V(D)J rearrangement that is different for of each the four domains that comprise this locus. For the ChIP-seq, input and immunoprecipitated DNA was given to The Scripps DNA Array Facility, where it was prepared for massively parallel sequencing on Illumina HiSeq2000.
Project description:In this study, we compare the binding pattern of CTCF at the T cell receptor alpha locus in different subsets of developing lymphocytes For the ChIP-seq, input and immunoprecipitated DNA was given to The Scripps DNA Array Facility, where it was prepared for massively parallel sequencing on Illumina Hi-Seq.
Project description:In this study, we compare the binding pattern of CTCF at the T cell receptor alpha locus in different subsets of developing lymphocytes For the ChIP-seq, input and immunoprecipitated DNA was given to The Scripps DNA Array Facility, where it was prepared for massively parallel sequencing on Illumina Genome Analyzer IIx.
Project description:In this study, we compare the binding pattern of CTCF at the T cell receptor alpha locus in different subsets of developing lymphocytes. For the ChIP-seq, input and immunoprecipitated DNA was given to The Scripps DNA Array Facility, where it was prepared for massively parallel sequencing on Illumina Genome Analyzer IIx.
Project description:Non-coding sense and antisense germline transcription within the immunoglobulin heavy chain locus precedes V(D)J recombination and has been proposed to be associated with Igh locus accessibility, although its precise role remains elusive. However, no global analysis of germline transcription throughout the Igh locus has been done. Therefore, we performed directional RNAseq, demonstrating the locations and extent of both sense and antisense transcription throughout the Igh locus. Surprisingly, the majority of antisense transcripts are localized around two PAIR elements in the distal IghV region. Importantly, long-distance loops measured by 3C are observed between these two active PAIR promoters and Eμ, the start site of Iμ germline transcription, in a lineage- and stage-specific manner, even though this antisense transcription is Eμ-independent. YY1-/- pro-B cells are greatly impaired in distal VH gene rearrangement and Igh locus compaction, and we demonstrate that YY1 deficiency greatly reduces antisense transcription and PAIR-Eμ interactions. ChIP-seq shows high level YY1 binding only at Eμ, but low levels near some antisense promoters. PAIR-Eμ interactions are not disrupted by DRB, which blocks transcription elongation without disrupting transcription factories once they are established, but the looping is reduced after heat shock treatment, which disrupts transcription factories. We propose that transcription-mediated interactions, most likely at transcription factories, initially compact the Igh locus, bringing distal VH genes close to the DJH rearrangement, which is adjacent to Eμ. Therefore, we hypothesize that one key role of non-coding germline transcription is to facilitate locus compaction, allowing distal VH genes to undergo efficient rearrangement. ChIP Seq YY1 vs. input control
Project description:The histone variant macroH2A1 and the poly(ADP-ribose) polymerase PARP-1 both regulate gene transcription by modulating chromatin structure and function. Of the two macroH2A1 splice variants, macroH2A1.1 and macroH2A1.2, the former is often suppressed in cancer and has the unique ability to interact with poly(ADP-ribose). Using ChIP-seq in primary lung fibroblasts, we demonstrate that macroH2A1 is incorporated into either of two spatially and functionally distinct types of chromatin; the first is marked by H3 K27 trimethylation, while the second contains a set of nine histone acetylations. MacroH2A1-regulated genes are involved in cancer progression are specifically found in macroH2A1-containing acetylated chromatin. Through the recruitment of PARP-1, macroH2A1.1 promotes the acetylation of H2B K12 and K120 which plays a key role in the regulation of macroH2A1 target genes in primary cells. The macroH2A1/PARP-1 pathway regulating H2B K12 and K120 acetylation is disrupted in cancer cells, in part, explaining macroH2A1’s role in cancer suppression. Three biological replicates of RNA-seq from cells expressing shRNA directed against macroH2A1 or luciferase as a control
Project description:Transcription factor binding locations by ChIP followed by high throughput sequencing. To build and validate an automated Chromatin Immunoprecipitation and high throughput Illumina sequencing pipeline
Project description:We report that full length TET1 (TET1-FL) overexpression fails to induce global DNA demethylation in HEK293T cells. The preferential binding of TET1-FL to hypomethylated CpG islands (CGIs) through its CXXC domain leads to its inhibited 5-hydroxymethylcytosine (5hmC) production as methylation level increases. TET1-FL-induced 5hmC accumulates at CGI edges, while TET1 knockdown induces methylation spreading from methylated edges into hypomethylated CGIs. However, TET1 can regulate gene transcription independent of its dioxygenase catalytic function. Thus, our results identify TET1 as a maintenance DNA demethylase that does not purposely decrease methylation levels, but specifically maintains the DNA hypomethylation state of CGIs in adult cells. hMeDIP-seq analysis of genomic 5-hydroxymethylcytosine in HEK293T cells overexpressing mTET1-CD, TET1-CD, mTET1-FL, or TET1-FL