Article

Methylation of H3K4 Is Required for Inheritance of Active Transcriptional States

Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
Current biology: CB (Impact Factor: 9.92). 02/2010; 20(5):397-406. DOI: 10.1016/j.cub.2010.01.017
Source: PubMed

ABSTRACT Maintenance of differentiation programs requires stability, when appropriate, of transcriptional states. However, the extent to which inheritance of active transcriptional states occurs from mother to daughter cells has not been directly addressed in unperturbed cell populations.
By live imaging of single-gene transcriptional events in individual cells, we have directly recorded the potential for mitotic inheritance of transcriptional states down cell lineages. Our data showed strong similarity in frequency of transcriptional firing between mother and daughter cells. This memory persisted for complete cell cycles. Both transcriptional pulse length and pulsing rate contributed to overall inheritance, and memory was determined by lineage, not cell environment. Analysis of transcription in chromatin mutants demonstrated that the histone H3K4 methylase Set1 and Ash2, a component of the methylase complex, are required for memory. The effects of Set1 methylation may be mediated directly by chromatin, because loss of memory also occurred when endogenous H3K4 was replaced by alanine. Although methylated H3K4 is usually associated with active transcriptional units, the modification was not required for gene activity but stabilized transcriptional frequency between generations.
Our data indicate that methylated H3K4 can act as a chromatin mark reflecting the original meaning of "epigenetic."

0 Followers
 · 
124 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Poised (bivalent) chromatin is defined by the simultaneous presence of histone modifications associated with both gene activation and repression. This epigenetic feature was first observed at promoters of lineage-specific regulatory genes in embryonic stem cells in culture. More recent work has shown that, in vivo, mammalian germ cells maintain poised chromatin at promoters of many genes that regulate somatic development, and that they retain this state from fetal stages through meiosis and gametogenesis. We hypothesize that the poised chromatin state is essential for germ cell identity and function. We propose three roles for poised chromatin in the mammalian germ line: prevention of DNA methylation, maintenance of germ cell identity and preparation for totipotency. We discuss these roles in the context of recently proposed models for germline potency and epigenetic inheritance.
    Development 10/2014; 141(19):3619-26. DOI:10.1242/dev.113027 · 6.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: REV1-deficient chicken DT40 cells are compromised in replicating G quadruplex (G4)-forming DNA. This results in localised, stochastic loss of parental chromatin marks and changes in gene expression. We previously proposed that this epigenetic instability arises from G4-induced replication fork stalls disrupting the accurate propagation of chromatin structure through replication. Here, we test this model by showing that a single G4 motif is responsible for the epigenetic instability of the BU-1 locus in REV1-deficient cells, despite its location 3.5 kb from the transcription start site (TSS). The effect of the G4 is dependent on it residing on the leading strand template, but is independent of its in vitro thermal stability. Moving the motif to more than 4 kb from the TSS stabilises expression of the gene. However, loss of histone modifications (H3K4me3 and H3K9/14ac) around the transcription start site correlates with the position of the G4 motif, expression being lost only when the promoter is affected. This supports the idea that processive replication is required to maintain the histone modification pattern and full transcription of this model locus.
    The EMBO Journal 09/2014; DOI:10.15252/embj.201488398 · 10.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Author Summary Three DNA polymerases replicate DNA in Eukaryotes. DNA polymerase α (Polα) initiates strand synthesis, which is performed by Polε and Polδ in leading and lagging strands, respectively. Not only the information encoded in the DNA, but also the inheritance of chromatin states is essential during development. Loss of function mutants in DNA polymerases lead to lethal phenotypes. Hence, hypomorphic alleles are necessary to study their roles beyond DNA replication. Here we identify a thermosensitive mutant of the Polδ in the model plant Arabidopsis thaliana, which bears an aminoacid substitution in the polymerase-domain. The mutants were essentially normal at 18°C but arrested development at 28°C. Interestingly, at 24°C we were able to study the roles of Polδ in epigenetic inheritance and plant development. We observed a tight connection between DNA replication stress and an increase the deposition of transcriptionally active chromatin marks in the SEPALLATA3 (SEP3) locus. Finally, we tested by genetic means that the ectopic expression of SEP3 was indeed the cause of early flowering and the leaf phenotypes by promoting the expression of FLOWERING LOCUS T (FT). These results link Polδ activity to the proper establishment of transcriptionally active epigenetic marks, which then impact the development of multicellular organisms.
    PLoS Genetics 02/2015; 11(2):e1004975. DOI:10.1371/journal.pgen.1004975 · 8.17 Impact Factor