Deep sequencing reveals complex spurious transcription from transiently transfected plasmids

Area of Science:

• Molecular Biology
• Genetics

Background:

• Transient plasmid transfection is a widely used method in mammalian cell culture for gene expression studies.
• Understanding the behavior and expression of transfected plasmids is crucial for accurate experimental outcomes.

Purpose of the Study:

• To investigate the transcriptional landscape of transiently transfected plasmids in cultured mammalian cells.
• To identify potential unintended consequences of plasmid transcription on experimental results.

Main Methods:

• Deep sequencing was employed to analyze the transcriptional products of transfected plasmids.
• Luciferase reporter assays were used to assess the impact of co-transfected plasmids on gene expression.

Main Results:

• Analysis revealed that the entire plasmid sequence is transcribed at varying levels.
• Some plasmids, particularly those with resistance cassettes like Kan/Neo, exhibited dose-dependent inhibition of reporter gene expression.
• A unique population of edited sense and antisense small RNAs was associated with the inhibitory effect.

Conclusions:

• The study reveals significant and unexpected transcriptional complexity from transiently transfected plasmids.
• Spurious transcription and resulting small RNAs can interfere with experimental readouts, such as reporter gene expression.
• Emphasizes the critical need for rigorous experimental controls when using transient transfection methods.