Results: 3

1.
Figure 1

Figure 1. Potential mechanisms linking environmental exposures to epigenetic effects. From: Epigenetics and environmental chemicals.

Environmental chemicals may modify multiple biological processes that affect epigenetic mechanisms, including DNA methylation, histone codes, and miRNA expression. These changes may, in turn, modify chromatin organization and condensation, gene expression, and affect disease risk.

A Baccarelli, et al. Curr Opin Pediatr. ;21(2):243-251.
2.
Figure 2

Figure 2. Example of possible mechanisms of gene-regulation by histone modifications. From: Epigenetics and environmental chemicals.

Modifications under histone methylases (HMTs), histone acetyltransferases (HATs) and histone deacetylases (HDACs) control alter gene expression. Modifications may generate a structure that contains bromo- and chromo-domains allowing the recruitment of ATP-dependent chromatin remodelling factors to open the chromatin. Effects of histone modifications on gene expression is dependent on the specific position of the chemical modification on the histone subunit.

A Baccarelli, et al. Curr Opin Pediatr. ;21(2):243-251.
3.
Figure 3

Figure 3. miRNA Processing and Activity. From: Epigenetics and environmental chemicals.

miRNAs are initially transcribed by RNA Polymerase II and expressed as a part of primary miRNAs (pri-miRNAs). The miRNA portion of the pri-miRNA transcript likely forms a hairpin with signals for dsRNA-specific nuclease cleavage. The dsRNA-specific ribonuclease Drosha digests the pri-miRNA in the nucleus to release hairpin that is called pre-miRNA (approximately 70 nt). Exportin-5 exports pre-miRNAs from the nucleus to the cytoplasm, where Dicer cleaves the pre-miRNA approximately 19 bp from the Drosha cut giving a mature miRNA. Each mature miRNA is complementary to a part of one or more messenger RNAs (mRNAs). The annealing of the miRNA to the mRNA(s) inhibits protein translation.

A Baccarelli, et al. Curr Opin Pediatr. ;21(2):243-251.

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