DNA Methylation Analysis of Steroid Hormone Receptor Genes

Abstract

Steroid hormone receptors (SHR) are important transcription factors for regulating different physiological and pathological processes. Their altered expression has been strongly associated to cancer progression. Epigenetic marks such as DNA methylation have been proposed as one of the regulatory mechanisms for SHR expression in cancer. DNA methylation occurs at CpG dinucleotides, which form clusters known as CpG islands. These islands are mostly observed at promoter regions of housekeeping genes, and their aberrant methylation in cancer cells is associated with silencing of tumor-suppressor gene expression. SHR genes are characterized for presenting alternative promoters with different CpG island content, which are prone to be methylated. The method of choice for studying DNA methylation is bisulfite sequencing, since it provides information about the methylation pattern at single-nucleotide level. The method is based on the deamination of cytosine residues to uracil after treatment with sodium bisulfite. The converted DNA is amplified by a polymerase chain reaction, cloned, and sequenced. Here, we describe a protocol for bisulfite sequencing suitable for analyzing different CpG regions in SHR genes.

Characterization of regulatory sequences in alternative promoters of hypermethylated genes associated with tumor resistance to cisplatin

“…As the mechanism associated with cisplatin resistance is multifactorial (1-3), our results suggest that the genes encoding cisplatin resistance harbor more than one option to initiate their transcripts to enhance the efficiency of mRNA production. It has been well documented that CGIs are prone to DNA methylation and this epigenetic mechanism is associated with gene silencing, initiation and maintenance of malignancy and drug resistance (6)(7)(8)(9)(37)(38)(39). Hypermethylation in CGIs and subsequent gene inactivation contributes to cisplatin resistance (9), as described earlier in this study.…”

Non-coding RNA-mediated epigenetic regulation of liver fibrosis

“…In mammalian DNA, the fifth position carbon of cytosine within cytosine guanine (CpG) dinucleotides can become methylated [82]. CpG dinucleotides exist throughout the genome and are usually heavily methylated and thus impede transcription of genes at those sites [83]. While these CpGs are relatively rare in the genome as a whole, they are often clustered in short stretches of DNA of 300-3000 base pairs (CpG islands) [84].…”

The potential disruption of estrogen and androgen homeostasis and adipocyte differentiation by metabolites of common airborne polychlorinated biphenyls

“…For example, concentrations of estradiol, estrone, and dehydroepiandrosterone have been found to be higher in breast and abdominal subcutaneous fat tissue than in the plasma of postmenopausal women [153]. In general, steroid hormones elicit biological responses by binding to steroid hormone receptors (e.g., glucocorticoid receptors, estrogen receptors, and progesterone receptors), and these receptors are involved in regulating the transcription of various genes [149][150][151]152].…”