tRNATrp as primer for RNA-directed DNA polymerase: structural determinants of function

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Avian oncornavirus replication relies on RNA-directed DNA polymerase (reverse transcriptase).
• Initiation of viral DNA synthesis requires a primer molecule, specifically tRNATrp.
• Understanding the interaction between reverse transcriptase and tRNATrp is crucial for deciphering viral replication mechanisms.

Purpose of the Study:

• To investigate the specific structural features of tRNATrp necessary for its interaction with avian oncornavirus reverse transcriptase.
• To differentiate the structural requirements for tRNATrp binding to the enzyme versus its function as a primer for DNA synthesis.

Main Methods:

• Enzyme-binding assays were used to assess high-affinity interactions between reverse transcriptase and various forms of tRNATrp.
• In vitro viral DNA synthesis assays were performed using intact and fragmented tRNATrp as primers.

Main Results:

• The entire primary structure and native conformation of tRNATrp are essential for stable binding to reverse transcriptase.
• Fragments of tRNATrp, specifically those containing the 3' terminal 27 nucleotides, can efficiently prime viral DNA synthesis.
• Altered conformations or significant structural modifications of tRNATrp prevent enzyme binding but not necessarily primer function.

Conclusions:

• Avian oncornavirus reverse transcriptase exhibits distinct structural recognition for tRNATrp binding and primer utilization.
• The 3' terminal region of tRNATrp plays a critical role in the specificity of initiating viral DNA synthesis.
• These findings provide insights into the molecular mechanisms governing the initiation of retroviral DNA replication.