Intron-containing Flippase optimized (InFlpo)
Expression-enhanced variant of Flpo recombinase containing SV40 T-antigen intron inserted within the open reading frame. The intron is spliced out during mRNA processing, yielding functional Flpo protein while providing improved expression efficiency through enhanced mRNA processing and nuclear export in mammalian cells.
Origin: Engineered from Flpo via SV40 T-antigen intron insertion
Characteristics
Contains SV40 large T-antigen intron inserted within the Flpo coding sequence at an optimized position that preserves protein function following splicing. Intron insertion increases steady-state mRNA levels through enhanced pre-mRNA processing, nuclear export, and transcript stability compared to intronless Flpo constructs. Maintains Cre-like recombination efficiency characteristic of Flpo while providing expression advantages in mammalian expression systems. Spliced mRNA produces functionally identical Flpo protein with preserved FRT site recognition (34 bp) and bidirectional recombination activity. Strategy follows established precedent of enhancing transgene expression through intron-mediated enhancement (IME) mechanisms documented for multiple mammalian expression systems.
Applications: Enhanced recombinase expression for applications requiring high Flpo levels in mammalian cells including transgenic animals, ES cell manipulations, and lentiviral/AAV vector systems. Particularly useful for FRT-mediated conditional mutagenesis strategies where robust recombinase expression is critical. Enables dual-recombinase genetic systems when combined with Cre-loxP for complex genomic engineering requiring orthogonal control. Applied in gene therapy vectors and iPSC reprogramming protocols where expression optimization is essential for efficient FRT site recombination.
Limitations: Requires functional splicing machinery in target cells, limiting utility in expression systems with compromised RNA processing. Larger coding sequence compared to standard Flpo due to intron inclusion may affect packaging constraints in size-limited viral vectors (particularly AAV). Intron sequence may introduce cryptic regulatory elements or alter mRNA secondary structure in unpredictable ways across different cellular contexts. Limited published characterization data compared to standard Flpo variant.