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PREFACE

Biochem. Cell Biol. 2016.94:iii-iii. Downloaded from www.nrcresearchpress.com by KYONGGI UNIV LIB on 02/11/16. For personal use only.

BCB Special Issue on Epigenetics The genome, made up of DNA, provides the general blueprint for each organism. However, the readout of the genome varies in each cell of the organism according to their differentiation and developmental states and in response to external cues. Such flexibility in how a cell interprets its genomic content is dictated by what is often referred to as “epigenetics”. Although the exact definition of epigenetics can be open to interpretation, it largely encompasses molecular events that modify the chemical modifications of the DNA itself, or of nucleosomal/linker histones, or events that influence chromatin topology. Such malleability is fascinating, and understanding how it is regulated is a pressing goal, considering the attractive therapeutic options it may provide for several human diseases. This special issue of Biochemistry and Cell Biology consists of 7 reviews and 1 original article focused on chromatin structure and epigenetics, a field featuring many strong Canadian and international scientists. Following the success of the 2nd Canadian Conference on Epigenetics held in June 2014, several speakers and participants were invited to contribute to this special issue, to highlight key areas of strength and discuss emerging thoughts stemming from this gathering of international epigenetics researchers. Leading the way is an excellent review of mammalian X chromosome inactivation, or XCI, by Thomas Dixon-McDougall and Carolyn Brown. XCI is a drastic example of how a whole chromosome can be epigenetically modified for the purpose of dosage compensation. Several interlinked mechanisms are discussed, involving the expression of the long non-coding RNA Xist and the subsequent spreading of heterochromatin histone marks. Next is an overview of how specific euchromatin histone methyltransferases (EHMTs) can influence cell differentiation, by Jamie Kramer. He focuses on two EHMTs, G9a and GLP, that are able to dimethylate histone 3 at lysine 9. Their diverse functions in cell differentiation are discussed, with particular focus on recent findings in Drosophila and rodent model systems. Marlee Ng and Peter Cheung contribute a very useful historical perspective of research on histone post-translational modifications and the “cross-talk” phenomenon at the nucleosome level.

Biochem. Cell Biol. 94: iii (2016) dx.doi.org/10.1139/bcb-2016-0004

They also discuss the experimental approaches, including reagents and tools to address the complexity of the nucleosome and its many chemical modifications. Mellissa Mann et al. propel us from the nucleosome to the more general regulation of chromatin architecture at imprinted domains. The latter consist of specialized genomic regions containing several genes expressed from only one, rather than two alleles. They argue that mono-allelic expression can be dictated by nuclear positioning of imprinted domains, for example to the nuclear lamina, the nucleolus or the nucleopore, and that dynamic positioning of chromatin might underlie tissue-specific imprinting. Abbas et al. present data regarding the epigenetic modulation of telomerase activity by sulforaphane (SFN) in prostate cancer cells. SFN is present in our diet and was proposed to confer chemo-preventive effects related to its histone deacetylase inhibitory actions. Epigenetic mechanisms can directly regulate gene transcription and splicing. Adam Scheidegger and Sergei Nechaev review evidence that external cues affecting the epigenetic profile of cells can contribute to context-dependent transcriptional programs by influencing promoter proximal RNA polymerase II pausing. Finally, Warns et al. and Davie et al. describe how chromatin topology can influence the process of alternative splicing. As guest editor, I hope that the contributions brought together in this special issue will provide a useful sampling of recent developments in this field of research. I sincerely wish to thank the editorial and production staff at Biochemistry and Cell Biology, the authors who contributed to this Special Issue on Epigenetics, as well as the individuals who spent time carefully reviewing the submitted works. We look forward to the 3rd Canadian Conference on Epigenetics in 2017 and again bring together our Canadian and international experts to share insights and advances in epigenetics research. Nathalie Bérubé Guest Editor Department of Biochemistry, University of Western Ontario, London, Ontario N6A 3K7, Canada.

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BCB Special Issue on Epigenetics.

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