Gene regulation involves the cellular process that aims to prevent and control the manner in which gene expression occurs. Gene regulation includes a range of mechanisms used by the cells to decrease or increase the production of specific products of the genes. Many sophisticated programs of gene expression are observed in biology that includes response to the environmental stimuli and triggering of other developmental pathways. Steps involving expression of genes can be controlled from the initiation of transcription, to processing the DNA, and to the mechanisms involved in the post translational modification of the proteins. Gene regulation is important for the prokaryotes, viruses and eukaryotes because it increases the adaptability and versatility of organism by cell to express the necessary protein when needed. In multicellular organisms, the process of gene regulation regulates processes such as morphogenesis and cellular differentiation that leads to creation of different types of cells that have different expression of gene profiles leading to production of different proteins.
Homeotic genes are those that are involved in the process of segmentation and in developmental sequences and patterns. The stages in which gene is regulated include chromatin domains, transcription, post transcriptional modification, RNA transport, translation and mRNA degradation. In eukaryotes, the accessibility of chromatin structure to a large part of the DNA depends on the chromatin that can be altered by histone modification fixed by ncRNA and DNA methylation. Certain modifications that regulate the expression of genes are inheritable and are called epigenetic regulation. DNA transcription depends of the structure and its packing indicates the frequency of transcription. Nucleosomes are the proteins responsible for supercoiling of the DNA and they are regulated by methylation and phosphorylation. The modifications are responsible for changes in expression of genes. Regulation of the transcription process controls the rate in which transcription occurs and how much of the mRNA is created. The transcription of genes by the use of RNA polymerase is controlled by five mechanisms.
Specificity factors disrupt the specificity of the enzyme RNA polymerase for given set of promoters reducing their binding capability. Specificity factors include sigma factors used in prokaryotic transcription. Repressors binds to the operator, coding the DNA strand sequences that overlap the promoter region, inhibiting the function of RNA polymerase along the strand leading to obstruction of the expression of genes. Lac operon is one of the repressors that bind to the operator. The gene transcriptional factors position the RNA polymerase at beginning of a protein, coding sequence and releases polymerase, which transcribes the mRNA. MicroRNA is one of the transcriptional factors regulating gene expression. The activators improve the interaction of the RNA polymerase and particular set of promoters that in turn encourage the expression of genes.
Enhancers are involved in looping the DNA by bringing the promoter to the initiation complex. They are commonly found in the eukaryotes than in the prokaryotes. Silencers silence gene expression when bound by particular transcription factors. Cells modulate the splicing, capping and addition of Poly (A) Tail processes in order to regulate the amount of mRNA translated to proteins. Translation of the mRNA is regulated by various mechanisms.
Gene regulation controls gene expression by various mechanisms that include even the use of housekeeping genes. Housekeeping genes play an important role in the process of gene expression because they are required in the maintenance of the basic cellular functions that are expressed by the cells in patho- physiological and normal conditions.
