An Exciting First for “Extinct” RNA

Of the standard macromolecules in biology, RNA seems to get the least fanfare. DNA tends to get credit as the repository of genetic information – the “blueprint” of life – while proteins make up much of the structure of our cells, tissues, and organs. However, RNA serves as the fundamental messenger between DNA and proteins, regulates gene expression, and can even contribute to the epigenetic regulation of DNA.

Types of RNA and Their Functions

RNA comes in various forms, each specializing in distinct tasks within the cellular machinery:

1. Messenger RNA (mRNA): mRNA carries the genetic code from the DNA in the nucleus of a cell to the ribosomes in the cytoplasm, where protein synthesis occurs. It acts as a copy of the DNA, guiding the assembly of amino acids into specific sequences to create proteins.
2. Transfer RNA (tRNA): Known as an adaptor molecule, tRNA brings amino acids to the ribosome during protein synthesis, matching them to the corresponding codons on the mRNA.
3. Ribosomal RNA (rRNA): Integral to the ribosome’s structure, rRNA forms the scaffold upon which protein synthesis takes place, providing the platform for mRNA and tRNA interactions.

Beyond Protein Synthesis: The Diverse Roles of RNA

While its involvement in protein synthesis is pivotal, RNA’s significance doesn’t end there. Emerging research unveils a myriad of additional roles:

• Regulation of Gene Expression: Small RNA molecules, such as microRNA and small interfering RNA (siRNA), play crucial roles in fine-tuning gene expression. They can silence or regulate the expression of specific genes by targeting mRNA and either blocking their translation or marking them for degradation.
• Epigenetic Modifications: Long non-coding RNAs (lncRNAs) contribute to epigenetic regulation, influencing chromatin structure and gene expression patterns without altering the underlying DNA sequence.
• Viral Defense Mechanism: CRISPR-Cas systems in bacteria and archaea utilize RNA molecules as guides to identify and destroy viral DNA, providing an adaptive immune response.

As you can see, RNA is involved in multiple aspects of cellular function and helps to regulate fundamental processes.

Analyzing RNA in the Tasmanian tiger
The Tasmanian Tiger, also known as the thylacine, is a creature that has fascinated biologists for decades. This carnivorous marsupial was not a tiger at all but rather a unique and enigmatic animal native to Tasmania, an island off the southern coast of Australia. With its dog-like appearance, striped back, and striking resemblance to a large marsupial wolf, the Tasmanian Tiger was hunted to extinction by farmers hoping to protect livestock.

The legacy of the Tasmanian Tiger has captivated the imagination of scientists, conservationists, and enthusiasts worldwide. Recently, researchers mapped the Tasmanian Tiger’s DNA, and some have even suggested trying to bring the species “back from the dead” by modifying the genes of a closely related species (the fat-tailed dunnart). However, simply knowing the genetic code of a species does not reveal information on gene expression. For that, scientists need to examine RNA expression in cells. To do this, researchers collected small samples from a museum specimen, isolated the RNA, and then compared the sequences to other known species. Using this technique, the researchers identified differences in the RNA molecules in the skin or muscle samples. They also discovered over 250 Tasmanian Tiger-specific microRNAs.

These results mark the first time that RNA has been collected and analyzed from an extinct animal species. Importantly, RNA is much less stable than DNA, which means that it tends to degrade much faster in samples that are not frozen or preserved. Hopefully these findings will lead to RNA analysis in other extinct species and allow for evolutionary biologists to compare RNA expression across a greater variety of organisms.

To read more about the RNA research in the Tasmanian Tiger see the research article here.