Chimeric thermostable DNA polymerases with reverse transcriptase and attenuated 3'-5' exonuclease activity

Area of Science:

• Molecular Biology
• Enzymology
• Biotechnology

Background:

• Accurate synthesis of full-length cDNA and subsequent PCR amplification from low-abundance RNA is challenging.
• Standard reverse transcription PCR (RT-PCR) often suffers from low fidelity and minimal mutations due to limitations of reverse transcriptases and DNA polymerases.

Purpose of the Study:

• To engineer novel DNA polymerases with enhanced reverse transcriptase and proofreading capabilities.
• To create "designer" DNA polymerases with attenuated 3"-5" exonuclease activity for improved RT-PCR performance.

Main Methods:

• Constructed a family of mutant DNA polymerases from a chimeric enzyme derived from Thermus species Z05 and Thermotoga maritima.
• Utilized structure-based tools to identify and mutate amino acid residues in the exonuclease domain.
• Characterized mutant enzymes for DNA polymerase activity, proofreading efficiency, and substrate specificity.

Main Results:

• Mutant DNA polymerases exhibited unaffected polymerase activity with a range of attenuated proofreading functions.
• Mutant enzymes showed a 5-15 fold stronger preference for mismatched substrates over single-stranded substrates compared to wild-type.
• Successfully generated a 1.7 kb amplicon from HIV-1 RNA using the engineered enzymes in an RT-PCR assay.

Conclusions:

• Engineered DNA polymerases offer tunable proofreading activity, enhancing accuracy in RT-PCR.
• These novel enzymes address limitations in synthesizing long amplicons from low-abundance RNA.
• The developed "designer" DNA polymerases represent a significant advancement for sensitive and accurate molecular biology applications.