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Comment
. 2013 Apr 30;110(18):7101-3.
doi: 10.1073/pnas.1305399110. Epub 2013 Apr 12.

Epigenetics: core misconcept

Mark Ptashne  1
Affiliations
Comment

Epigenetics: core misconcept

Mark Ptashne. Proc Natl Acad Sci U S A. .
No abstract available

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Conflict of interest statement

The author declares no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Establishment and maintenance of a positive feedback loop in a bacterium. Represented here are a few of the ca 50 phage genes of the bacteriophage lambda. The initial rightwards transcript extends through gene cII. The CII protein, a transcription activator, then activates a leftwards transcript that includes the gene cI. The cI protein, another transcription activator, activates expression of its own gene (a positive feedback reaction) as it represses rightwards transcription, including that of cII. This feedback loop, once established, is stable for very many cell divisions as the continuously produced CI protein (called the lambda repressor) is distributed to daughter cells. The bacteria are “lysogenic:”exposure to a signal (e.g., UV light) inactivates the repressor, previously silent phage genes areexpressed, and the cell lyses with the production of many new phage particles. PRE, PRM, and PR designate the “establishment,” “maintenance,” and “rightwards” promoters, respectively. (Reproduced with permission from refs. and .)
Fig. 2.
Fig. 2.
Establishment and maintenance of expression of terminal differentiation genes required to define a specific type of sensory neuron in a nematode. A series of gene regulatory events (not shown) produces, transiently, an activator depicted as a blue ball. That activator binds to the establishment cis-regulatory sequence (blue cube), and activates transcription of a terminal selector gene. The latter, another transcription activator, then maintains transcription of its own gene as it activates genes required for specific functions of the neuron. (Reprinted from ref. , Copyright 2011, with permission from Elsevier.)
See this image and copyright information in PMC

Comment on

  • Epigenetics.
    Williams SC. Williams SC. Proc Natl Acad Sci U S A. 2013 Feb 26;110(9):3209. doi: 10.1073/pnas.1302488110. Epub 2013 Feb 15. Proc Natl Acad Sci U S A. 2013. PMID: 23417306 Free PMC article. No abstract available.

References

    1. Williams SCP. Epigenetics. Proc Natl Acad Sci USA. 2013;110(9):3209. - PMC - PubMed
    1. Davidson EH. The Regulatory Genome: Gene Regulatory Networks in Development and Evolution. Burlington, MA: Academic; 2006.
    1. Ptashne M, Gann A. Genes and Signals. Cold Spring Harbor, NY: Cold Spring Harbor Lab Press; 2002.
    1. Ptashne M. A Genetic Switch (Third Edition): Phage Lambda Revisited. Cold Spring Harbor, NY: Cold Spring Harbor Lab Press; 2004.
    1. Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell. 2006;126(4):663–676. - PubMed

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