Role of Hormones in gene regulation

Hormones are important factors in the gene regulatory network, and their role is of functional importance for a cell. Hormones regulate development in many different ways including developmental timing, tissue specification, and differentiation. This article explores the role of hormones in cell division as it relates to genes regulation and development.

What are Genes?

A gene is the basic unit of heredity and inheritance. A gene contains a specific set of characters that determine the phenotype (the visible characteristics) of a cell, organism, group of organisms, or species. The genetic information in genes determines each organism’s characteristics. Genes are composed of bases called nucleotides that consist of a combination of two types referred to as DNA (deoxyribonucleic acid) or RNA (ribonucleic acid). In the nucleotide strand of DNA, the sequence is arranged in spirals and circles called base pairs arranged in a complementary fashion to produce genetic information for each gene. The 3 standard codons may be used to specify amino acids.

What are hormones?

Hormones are chemical substances produced by endocrine tissues and secreted into the blood to control cell growth, reproduction, and metabolism. In animals they act at many different sites in the body to influence a wide range of biological functions. Among their functions are regulation of growth, development, energy metabolism, behaviour, and emotional state. 

Role of Hormones’ in Gene Regulation:

Hormonal activity is controlled by complex feedback mechanisms that regulate the release of hormones into the systemic circulation. Hormone secretion can be strongly affected by psychological and physical factors, even more so than other biological processes. For example, stress is among the most powerful inducers of hormone release. The hormonal changes brought about by stress are probably important factors in the development of many diseases, including cardiovascular disease and cancer. The hormones are secreted in response to a stimulus and act as chemical messengers that travel through the bloodstream to major target organs or tissues. Once at their sites of action, they either stimulate or inhibit the synthesis of enzymes and other proteins, leading to alterations in cell function. In addition, hormones also support the structural components of cells. The most important hormones in gene regulation are described below:  Retinoic acid (RA) is a derivative of vitamin A that induces cells to differentiate by activating specific gene transcription programs during development. In many cell types, RA also acts on programmed cell death. 

The major control of growth is mediated by the release of insulin-like growth factor 1 (IGF-1) from the liver. Endocrine systems regulate insulin and IGF-1 concentrations, with hepatic secretion promoting growth and hypoglycemia and inhibition causing growth arrest. Growth hormone (GH) is secreted by the pituitary gland in response to GH-releasing hormone (GHRH). GH stimulates muscle tissue to grow, primarily in children and adolescents who are growing rapidly but also in adults during periods of rapid weight gain or loss. GH stimulates protein synthesis, including growth hormone–binding protein (GHBP), which binds GH.

Gene Expression:

The process in which DNA’s information is used to make proteins, which in turn regulate gene expression. A cell has two copies of each gene (one inherited from the mother and one from the father). A cell uses only one copy of a gene. When a cell divides into two new cells, each new cell gets a copy of the same genetic information. The process by which a nucleus or cytoplasmic membrane produces an RNA molecule is called transcription. This process requires an enzyme called RNA polymerase, along with other assorted factors, and begins at specific DNA sequences referred to as promoters. These transcription sites can be very specific in their location and can even begin at internal sites within a larger gene (known as introns).

Regulation of Gene Expression:

The regulation of gene expression is accomplished in several ways, the most common of which is by controlling the rate at which transcription takes place. In all cases, transcription is slowed or halted when a factor binds to the promoter sequence upstream from where elongation begins. Another method involves preventing the binding of RNA polymerase to promote elongation; this may involve such chemicals as metal ions and adenosine triphosphate (ATP).

Conclusion:

Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. Regulation of gene expression, therefore, involves control over this synthesis. Different types of regulation are categorised by the nature of the controlling signal: whether it is an internal or external signal and how it acts to alter transcription. Potential mechanisms to control gene expression include transcription factors and modifications of the chromatin structure.