Question

An example of free radical modification of RNA is a. 8-hydroxyguanosine (8-OHG) b. 4-hydroxy-2-nonenal (HNE) c. 3-nitrotyrosine (NT) d. 8-hydroxy-2'-deoxyguanosine (8-OHdG)

Short answer

a. 8-hydroxyguanosine (8-OHG) b. 4-hydroxy-2-nonenal (HNE) c. 3-nitrotyrosine (NT) d. 8-hydroxy-2'-deoxyguanosine (8-OHdG) Answer: a. 8-hydroxyguanosine (8-OHG)

Step-by-step solution

Understand Free Radical Modification of RNA

Free radicals are molecules with an unpaired electron, making them highly reactive and able to cause damage to other molecules such as nucleic acids (DNA and RNA). In the context of RNA, free radical modification refers to the process by which free radicals attack and modify RNA molecules, leading to the formation of chemically altered products.

Identify the Correct Option

Now that we understand free radical modification of RNA, let's analyze each of the given options: a. 8-hydroxyguanosine (8-OHG): This is a modified form of guanosine, one of the four building blocks of RNA, that results from the reaction of guanosine with free radicals. Therefore, this option is an example of free radical modification of RNA. b. 4-hydroxy-2-nonenal (HNE): This is a product of lipid peroxidation and is not directly related to RNA modification. This option is not an example of free radical modification of RNA. c. 3-nitrotyrosine (NT): This is a product formed when tyrosine, an amino acid, reacts with reactive nitrogen species. Since this is related to protein modification and not RNA, this option is not an example of free radical modification of RNA. d. 8-hydroxy-2'-deoxyguanosine (8-OHdG): This is a modified form of 2'-deoxyguanosine, which is one of the building blocks of DNA, not RNA. Thus, this option is an example of free radical modification of DNA, not RNA.

Choose the Correct Answer

Based on the analysis in Step 2, we can conclude that option a (8-hydroxyguanosine) is the correct answer as it is an example of free radical modification of RNA.

Key concepts

8-hydroxyguanosine

8-hydroxyguanosine (8-OHG) is an interesting molecule that results from the oxidative modification of guanosine, one of the four main nucleosides found in RNA. When RNA is exposed to oxidative stress, reactive oxygen species (ROS) can attack the guanosine bases and introduce an additional hydroxyl group, creating 8-OHG. This modification is significant because it can affect the normal function of RNA. It often leads to errors in protein synthesis if not repaired. This type of damage can ultimately contribute to various diseases and developmental issues. To understand 8-OHG's role in cellular processes, it's helpful to consider:

• Its potential to cause mutations during replication.
• Its relationship with cellular oxidative stress levels.
• The existence of repair mechanisms in cells to fix this type of damage.

RNA Damage

RNA damage refers to any alteration in the structure or function of RNA molecules. Such modifications might be a result of environmental stressors or intrinsic cellular processes. When free radicals, particularly reactive oxygen species, interact with RNA, they can lead to oxidative damage. This results in the alteration of the native structures of nucleobases like guanosine. Damage to RNA can have several consequences:

• Disruption of protein synthesis, as RNA is crucial in translating genetic information to proteins.
• Triggering of stress response mechanisms within the cell to mitigate the effects of such damage.
• Potential contribution to diseases such as neurodegenerative disorders, where RNA regulation is critical.

Living cells have evolved mechanisms to repair or compensate for RNA damage, but when these processes fail, it can lead to significant cellular dysfunction.

Reactive Oxygen Species

Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen. They are a natural byproduct of the normal metabolism of oxygen but can increase dramatically during times of environmental stress. Despite their potentially harmful effects, ROS play crucial roles in cell signaling and homeostasis. However, an imbalance in ROS levels can lead to oxidative stress, causing damage to crucial biomolecules, including lipids, proteins, and nucleic acids like RNA. Key aspects of ROS to understand include:

• Their source: both from endogenous (e.g., mitochondria) and exogenous (e.g., pollution, UV light) factors.
• Their role in signaling pathways that help regulate cell function.
• The antioxidant defense systems that protect cells from excessive ROS.

Managing ROS levels is vital for maintaining cellular integrity and preventing oxidative damage that can contribute to aging and various diseases.