UT researchers have a fix for a biological glitch that will improve diagnoses of genetic conditions

Danielle Ransom

UT researchers have created a new enzyme that allows for more accurate diagnoses of genetic conditions.

The team, led by Jared Ellefson, a postdoctoral fellow in UT Austin’s Center for Systems and Synthetic Biology, and Andy Ellington, a molecular biosciences professor, published their findings in the journal Science in June.

The new enzyme is a reverse transcriptase. Reverse transcription is a process that creates single-stranded DNA from an RNA template. This process is commonly associated with retroviruses, and is done by reverse transcriptase enzymes. 

Scientists currently use reverse transcription to better understand genetic diseases. The new enzyme is an improvement on currently used reverse transcriptases because it can fix any errors that occur throughout the reverse transcription process. 

“Reverse transcriptase enzymes in any form don’t have a proofreading domain so they are inherently error-prone,” said Raghav Shroff, a molecular bioscience graduate student and co-author of the study. “As a lab, we questioned how could we add or modify existing proteins to give them another function.”

The main challenge for the team was to evolve a DNA polymerase, an enzyme that creates DNA molecules, to accurately fit RNA templates by forcing the DNA to read these templates during transcription. 

“We started with a DNA polymerase and they can only read DNA. They can’t read RNA,” Shroff said.

DNA polymerase was used because of its ability to proofread its transcripts, which naturally-occurring reverse transcriptases can’t do. 

“We used a directed evolution technique to force the DNA polymerase to read an RNA template, which forces the DNA polymerase to act as a reverse transcriptase,” Shroff said.

The technique, called compartmentalized self-replication, works by causing the DNA polymerase to copy its own encoding gene and evolve the ability to utilize an RNA template. They continued using this technique until the polymerase could read RNA.

The final product was a new enzyme called Reverse Transcription Xenopolymerase, which not only copies RNA transcripts, but also fixes errors along the way. Shroff said this enzyme is revolutionary because it will allow scientists to create more accurate DNA transcripts from RNA.

This new enzyme is far more precise than current RNA retroviral methods.

“The proofreading domain can now cut out the incorrect base and insert the correct base,” Shroff said.

Because so many diseases are identified using genetic information, this new method could be a useful tool for more accurate diagnoses.

“As we move towards an age of personalized medicine where everyone’s transcripts will be read out almost as easily as taking a pulse, the accuracy of the sequence information will become increasingly important,” Ellington said in a press release.

This new enzyme also has the potential to help researchers better understand genetic disorders.

“The significance of this is that we can now also copy large amounts of RNA information found in modern genomes, in the form of the RNA transcripts that encode almost every aspect of our physiology,” Ellington said. “This means that diagnoses made based on genomic information are far more likely to be accurate.”