Polypurine tract primer generation and utilization by Moloney murine leukemia virus reverse transcriptase

Area of Science:

• Molecular Biology
• Virology
• Enzymology

Background:

• Reverse transcriptase (RT) is crucial for retroviral replication.
• RNase H activity of RT cleaves viral RNA, including the polypurine tract (PPT).
• PPT serves as a primer for plus-strand DNA synthesis.

Purpose of the Study:

• Investigate how primer length and sequence influence PPT generation and utilization.
• Elucidate the mechanisms of reverse transcriptase in processing the PPT primer.
• Understand the interplay between RNase H and polymerase activities of RT.

Main Methods:

• Utilized short hybrid RNA-DNA substrates with or without the PPT.
• Evaluated cleavage, extension, and binding kinetics by reverse transcriptase.
• Assessed activities of isolated RNase H and polymerase domains of RT.

Main Results:

• Primer length significantly impacts susceptibility to RNase H cleavage.
• RNA substrates with specific 3' ends were efficiently cleaved to generate the PPT primer.
• Substrates lacking the PPT were cleaved nonspecifically and extended inefficiently.
• Specific PPT generation and 5'-end-directed cleavages were kinetically favored.

Conclusions:

• Reverse transcriptase selectively generates and utilizes the PPT primer.
• Primer length and sequence are critical for efficient PPT processing.
• Specific cleavage events are favored to ensure proper initiation of plus-strand DNA synthesis.