In the pursuit of unraveling the mysteries of aging, researchers have long been intrigued by the intricate workings of our genetic code. Among the various cellular processes involved, DNA transcription, the conversion of DNA to RNA, has emerged as a focal point of investigation. Recent studies have shed light on the fascinating connection between DNA transcription, aging, and lifespan extension. In a groundbreaking paper
published in Nature
, researchers delve into the molecular mechanisms underlying animal aging and provide insights into potential preventive measures (Debès C, Papadakis A, Grönke S, et al. Ageing-associated changes in transcriptional elongation influence longevity. Nature
, 2023: 616:814–821 https://doi.org/10.1038/s41586-023-05922-y). Their findings reveal a novel aspect of aging, characterized by an age-related escalation in the pace at which DNA is transformed into RNA and its impact on subsequently translated functional proteins.
Unraveling the Transcription Process
To grasp the significance of DNA transcription, it is important to understand its process in simplistic terms. Functionally, DNA serves as a library filled with books containing the instructions for building and maintaining our bodies. DNA transcription can be likened to the process of translating those books into a language that our cells can understand. This process relies on a complex of molecules transcribing the genetic information into RNA molecules. These RNA molecules then serve as blueprints for the translation of proteins that are crucial for various cellular functions.
Histones are a type of protein found in chromosomes. They bind to DNA, help to give chromosomes their shape, and help to control the activity of genes.
The initial stage of transcribing DNA into RNA is more complex than meets the eye, and maintaining its fidelity could be vitally important to aging. To ensure efficient use of space, DNA is tightly packaged around a cluster of proteins known as histones, ultimately forming a structure referred to as the nucleosome. Imagine the nucleosome as a beaded necklace. Each bead on the necklace represents a histone protein, while the string that holds the beads together represents the DNA strand. Beyond the spatial efficiency this design provides, the nucleosome acts as a safeguard, protecting the genetic information from damage and adventitious DNA transcription events. Moreover, as a result of DNA being tightly wrapped around histones, access by transcribing machinery is impaired, and this acts as a meditated regulator of gene expression.
The process of unwinding DNA and priming it for transcription requires a collaborative effort from a multitude of proteins. At the heart of this operation lies RNA polymerase II (Pol II), a molecular complex that traverses along the DNA strand, resulting in an early form of RNA aptly known as pre-RNA.
The research conducted by Debès et al. took a comprehensive approach, examining transcriptional processes across multiple organisms, including nematodes, fruit flies, mice, rats, and humans. Using a technique called RNA sequencing, the team measured the speed of Pol II as it traveled along the DNA in cells of different ages. Their findings revealed a universal trend: Pol II speed increased with age across all species and tissues examined. Regardless of the specific gene or tissue, this acceleration of Pol II emerged as a consistent marker of aging.
The Link Between Transcription Speed and Errors
Along with the increase in Pol II speed came potential errors in the crucial process of splicing, which edits pre-RNAs before they can be translated into functional proteins. Maintaining an optimal speed is crucial for accurate splicing, and any deviation can result in faulty translations of proteins. The authors observed that the risk of bad translations increased with the acceleration of Pol II speed, a phenomenon previously associated with advanced age and shortened lifespan. These findings shed light on the delicate balance required for proper splicing and the potential consequences when that balance is disrupted.
Interventions to Slow Aging
Building upon their discoveries, the researchers devised interventions to counteract the age-related increase in Pol II speed. By comparing human umbilical vein cells and lung cells, they uncovered that as cells age, the nucleosomes responsible for regulating Pol II speed slowly unwind and fall apart. This structural change makes it easier for Pol II to slide along the DNA strand, leading to a boost in transcriptional speed. To test their theory, the team genetically inserted two types of histone proteins into human cells in Petri dishes. This modification created additional “speed bumps” for Pol II, effectively slowing down its pace.
The intervention yielded promising results. Cells with additional histone proteins displayed a decreased likelihood of becoming senescent, a state commonly associated with aging. Furthermore, fruit flies, a widely used model organism for longevity research, showed a notable increase in lifespan when subjected to this genetic modification.
The intricate process of DNA transcription has revealed its profound impact on the aging process and lifespan. The research conducted by Debès et al. provides significant insights into the molecular mechanisms underlying animal aging, highlighting the age-related increase in Pol II speed as a universal marker of aging. Pol II has already been extensively studied in cancer therapy, with several medications tested and approved. These new findings hold significant promise for the development of novel anti-aging drugs and the potential repurposing of existing medications. Leveraging this knowledge, researchers could explore the possibility of repurposing these medications for longevity research, opening up exciting new avenues for anti-aging interventions, and moving one step closer to unlocking the secrets of longevity and promoting healthy aging.