Epigenetic Code

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Epigenetic code is a term from the scientific field of epigenetics . Epigenetic codes are hypothetical or actual mapping rules ( codes ) that are intended to describe the rules for epigenetic processes. Due to the current state of knowledge, the existence of an epigenetic code in the sense of a generally defined, uniform set of rules must still be viewed as a hypothesis (see also histone code hypothesis )

Example histone code

An important example of an epigenetic code is the histone code showing the effect of chemical modifications to histones (specific protein - molecules ) on the structure and the information release of genetic material ( DNA should be written). With the structure is meant that in living beings with a cell nucleus , such. B. in humans, the genetic material can be relatively "loose" (little packed chromatin ) or more twisted (tightly packed chromatin or chromosomes ). The release of information means that the individual genes (sections with a defined function) are used to different degrees ( gene activity ) , depending on the effect of the histones .

Histone code and DNA methylation pattern

The histone code is closely related to DNA methylation patterns. DNA methylation is a form of chemical modification of nucleotides (the individual building blocks of genetic material). The DNA methylation influences the binding of histones or the modified variants. The histone modifications (the chemical changes to the histones) influence the activity of the genes depending on the degree of methylation of the DNA . Among other things, genes become active or inactive, which form proteins that feed back to DNA methylation or to histone modifications. This is for example in Jin et al. (2011).

Epigenetic Code and Epigenome

The epigenetic code is closely related to the epigenome . While the term epigenome is intended to capture the epigenetic states in a cell or tissue (mostly histone modifications, DNA methylation patterns and chromatin structures), the corresponding code (or its decoding) is used to identify the origin and development of an epigenome and its effects to understand the phenotype of the cell, tissue or organism .

Genetic and Epigenetic Code

The genetic code is a one-dimensional code. This means that it describes the rules for input and output in one direction:
If a certain nucleotide sequence consisting of three nucleotides is present in the valid context, then this information is converted into the incorporation of a certain amino acid in a protein (simplified representation). So you can write ATG -> M , meaning that the triplet sequence of adenine, thymine and guanine leads to the incorporation of methionine into the resulting peptide chain. Epigenetic codes are multidimensional. As described above, they must record repercussions and influencing conditions. This makes an epigenetic code very complex.

application

The current state of knowledge means that the efforts of epigenetics focus on the elucidation of epigenetic rules. There is hope that a known epigenome and a known epigenetic code can be used together in a manner similar to that of a known genome with a known genetic code. However, if you consider that the genome and genetic code are by no means all of the necessary information (promoters, open reading hypotheses, introns, etc.) to comprehensively interpret the genome, one can assume that the application of epigenetic codes on epigenome is an enormous challenge. Presumably it is necessary to include all biologically relevant types of molecules in the consideration. For example, data that arise from researching the histone code is kept in a database for the detection of the histone modifications by corresponding proteins.

Individual evidence

  1. ↑ B. Jin, Y. Li, KD Robertson: DNA methylation: superior or subordinate in the epigenetic hierarchy? In: Genes & cancer. Volume 2, number 6, June 2011, pp. 607-617, doi : 10.1177 / 1947601910393957 , PMID 21941617 , PMC 3174260 (free full text).
  2. ^ Bryan M. Turner: Defining an epigenetic code. In: Nature Cell Biology. 9, 2007, pp. 2-6, doi : 10.1038 / ncb0107-2 .
  3. ↑ R. Chahwan, SN Wontakal, S. Roa: The multidimensional nature of epigenetic information and its role in disease. In: Discovery medicine. Volume 11, Number 58, March 2011, pp. 233-243, PMID 21447282 (review).
  4. ↑ M. Wang, MW Mok, H. Harper, WH Lee, J. Min, S. Knapp, U. Oppermann, B. Marsden, M. Schapira: Structural genomics of histone tail recognition. In: Bioinformatics. Volume 26, Number 20, October 2010, pp. 2629-2630, doi : 10.1093 / bioinformatics / btq491 , PMID 20739309 , PMC 2951094 (free full text).