Substrate specificity of Ty1 integrase

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The Saccharomyces cerevisiae retrotransposon Ty1 integrates into the host genome via its encoded integrase (IN) protein, found within cytoplasmic virus-like particles (VLPs).
• Understanding the precise mechanisms and sequence specificities of Ty1 IN is crucial for elucidating retrotransposon dynamics and genome stability.

Purpose of the Study:

• To investigate the in vitro activity and sequence preferences of purified Ty1 integrase (IN) and VLP-associated IN.
• To compare the integration activity of Ty1 IN on various substrate end configurations and identify key sequence determinants.

Main Methods:

• Oligonucleotide integration assays using purified recombinant Ty1 IN and VLP-associated IN.
• Utilized substrates with wild-type and altered Ty1 long terminal repeat (LTR) donor end sequences.
• Assessed both forward integration and reverse disintegration reactions.

Main Results:

• Ty1 IN exhibited a preference for blunt-end substrates terminating in A:T pairs over G:C pairs or 3' dideoxyadenosine.
• VLP-associated IN also preferred donor strands with an adenosine terminus.
• Ty1 IN activity was sensitive to nucleotide removal from staggered-end substrates, particularly from the complementary strand, and lacked the 3' dinucleotide cleavage characteristic of retroviral integrases.

Conclusions:

• Ty1 IN demonstrates sequence preferences in vitro, favoring specific terminal nucleotides and end structures.
• The integration mechanism differs from retroviral integrases, notably lacking 3' dinucleotide cleavage.
• Both recombinant IN and VLP-associated IN catalyze disintegration with similar sequence preferences as integration.