Key Difference – Positive vs Negative Gene Regulation
Gene regulation is a process of controlling geneswhich are expressed in the cells’ DNA. By controlling the gene expression, cells can control the production of functional proteins in the cells. Some genes are turned on while some are turned off according to the requirement. Gene regulation can be performed starting from the availability of DNA, production of mRNA to the processing of proteins. Different genes are controlled at different points in gene expression; for example, chromatin structure regulation, transcriptional level, and RNA processing level, etc. Positive and negative gene regulation are two gene regulating processes in which genes are expressed, and genes are suppressed, respectively. The key difference between positive and negative gene expression is that in positive gene regulation, transcriptional factor binds to the promoter of the gene and facilitates the binding of RNA polymerase to transcript the gene while in negative gene regulation, a repressor protein binds with the operator of the gene and prevents gene expression.
CONTENTS
1. Overview and Key Difference
2. What is Positive Gene Regulation
3. What is Negative Gene Regulation
4. Side by Side Comparison – Positive vs Negative Gene Regulation
5. Summary
What is Positive Gene Regulation?
Transcription is the initial step of gene expression. It only happens when RNA polymerase is attached to the gene. If this attachment fails, gene expression is not possible; hence, gene expression can be regulated. The binding of RNA polymerase with DNA is induced by the transcription factors present in the nucleus. A transcription factor is a protein which is an integral part of the gene expression. This factor should bind with the promoter region of the gene to activate gene expression by recruiting RNA polymerase to the template DNA. Transcription factor can work alone or with other proteins to regulate the rate of gene expression by promoting or blocking RNA polymerase enzyme, which catalyzes the mRNA synthesis.
Positive gene regulation is a process which drives genes to express and create proteins they encoded. It happens due to the binding of a transcription factor to the promoter and recruiting RNA polymerase to initiate transcription. cAMP-CRP complex is an activator for positive regulation of β-galactosidase gene.
Figure 01: Positive Gene Regulation
What is Negative Gene Regulation?
Gene expression can be blocked by certain proteins present in the cells. They act as inhibitors of the gene activation. They are known as repressor proteins. A repressor is a protein which binds to the operator site of the gene or promoter and stops the transcription. Hence, negative gene regulation is a process in which genes are prevented from expressing and producing proteins. Binding of the repressor proteins into the promoter region of the gene inhibits the gene by blocking the RNA polymerase at the beginning. The respective gene can be expressed to make the protein only when the repressor is absent. Tryptophan is a common repressor molecule involved in negative gene regulation.
Figure 02: Negative Gene Regulation
What is the difference between Positive and Negative Gene Regulation?
Positive vs Negative Gene Regulation |
|
| Positive gene regulation is a process which makes the genes express and synthesize proteins. | Negative gene regulation is a process which represses gene expression. |
| Factors Involved | |
| Positive control is done by activator or the transcription factor binding with the promoter region. | Negative control is done by the repressor protein binding to the promoter or operator site of the genes. |
| Recruitment of RNA Polymerase | |
| RNA polymerase is recruited to initiate transcription. | RNA polymerase is not recruited to initiate transcription. |
Summary – Positive vs Negative Gene Regulation
Cells contain their genetic information as genes hidden in the DNA. Genes express and synthesize proteins, and this process is known as gene expression. However, gene expression is controlled in the cells to avoid wasting energy and raw materials in the synthesis of proteins which are unwanted. Gene regulation can be done in two ways: positive and negative gene regulation. In positive gene regulation, genes are expressed due to the binding of a transcription factor to the promoter of the gene. In negative gene regulation, genes are not expressed due to the binding of repressor proteins to the operator site of the gene. This is the main difference between positive and negative gene regulation.
Reference:
1. “Control of Gene Expression.” Biology Reference. N.p., n.d. Web. 25 Apr. 2017
2. Wang, Y., J. Xu, T. Pierson, B. W. O’Malley, and S. Y. Tsai. “Positive and negative regulation of gene expression in eukaryotic cells with an inducible transcriptional regulator.” Gene therapy. U.S. National Library of Medicine, May 1997. Web. 25 Apr. 2017