Ty3 reverse transcriptase complexed with an RNA-DNA hybrid shows structural and functional asymmetry

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Retrotransposons are mobile genetic elements replicating via RNA intermediates.
• Reverse transcriptase (RT) enzymes with DNA polymerase and ribonuclease H (RNase H) activities are crucial for retrotransposon replication.
• Structural data for long terminal repeat (LTR)-containing retrotransposon RTs are scarce compared to retroviral RTs.

Purpose of the Study:

• To determine the first crystal structure of a Saccharomyces cerevisiae long terminal repeat (LTR)-containing retrotransposon RT.
• To elucidate the structural basis of Ty3 RT function and its comparison to retroviral RTs.

Main Methods:

• X-ray crystallography to obtain the complex structure of Ty3 RT.
• Biochemical assays to investigate enzyme activities.

Main Results:

• The first crystal structure of Ty3 RT complexed with its RNA-DNA hybrid substrate was determined.
• Ty3 RT exhibits an asymmetric homodimeric architecture, unlike its retroviral counterparts.
• Substrate binding induces a specific homodimeric assembly.
• Biochemical data indicate that RNase H and DNA polymerase activities are localized to distinct subunits within the homodimer.

Conclusions:

• Ty3 RT possesses a unique asymmetric homodimeric structure crucial for its function.
• The findings provide novel insights into the replication mechanisms of LTR-containing retrotransposons.
• This study lays the groundwork for future structural and functional studies of retrotransposon RTs.