A Ty1 integrase nuclear localization signal required for retrotransposition

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Retrotransposition of Ty1 elements in Saccharomyces cerevisiae is crucial for genome integrity.
• Ty1 integrase (IN) mediates the insertion of Ty1 cDNA into the host genome.
• Nuclear envelope integrity in yeast necessitates specific mechanisms for nuclear import of cytoplasmic components.

Purpose of the Study:

• To identify and characterize the nuclear localization signal (NLS) in Ty1 integrase (IN).
• To determine the role of IN nuclear localization in Ty1 transposition.
• To investigate the functional domains of Ty1 IN.

Main Methods:

• Site-directed mutagenesis of Ty1 IN to disrupt the putative NLS.
• Assays for Ty1 transposition, reverse transcription, and in vitro catalytic activity.
• Intragenic complementation experiments to assess IN multimerization and domain function.

Main Results:

• A bipartite NLS was identified in Ty1 IN, essential for directing IN to the nucleus.
• Mutations abolishing nuclear localization inactivated transpositional integration but not reverse transcription or catalytic activity.
• Ty1 IN nuclear localization does not require other Ty1-encoded proteins.
• Evidence suggests Ty1 IN functions as a multimer with distinct domains for integration and nuclear localization.

Conclusions:

• The identified NLS is critical for Ty1 IN nuclear import and subsequent integration into the yeast genome.
• Nuclear targeting of the preintegration complex via an IN NLS may be a conserved mechanism in retrotransposons and retroviruses.
• Understanding IN nuclear localization provides insights into the regulation of retrotransposition in non-dividing cells.