# Co-Transfected Plasmids Enhance Transient Expression of Reporter Genes

## TL;DR

Co-delivering plasmids with reporter genes boosts their short-term expression in cells, possibly due to competition for cellular resources like histones.

## Contribution

The study reveals that co-transfected plasmids enhance transient reporter gene expression through competition for histone interactions.

## Key findings

- Co-transfected plasmids enhance transient reporter gene expression across multiple cell types.
- The enhancement occurs during simultaneous DNA delivery and is not mediated by cytokine induction.
- Histone deacetylase inhibition with Pracinostat boosts transient gene expression dose-dependently.

## Abstract

Transient DNA transfection is routinely used to study gene function and elucidate the regulation of biological pathways, and it is also widely applied in biotechnology for large-scale recombinant protein production. The results of recent studies involving mammalian cells have highlighted that competition for cellular resources during gene expression can bias data interpretation, directly affecting co-transfection experiments. In this study, our results showed that co-transfected plasmids markedly enhance transient—but not stable—expression of various reporter genes across different cell types. The enhancement of transient reporter gene expression by additional plasmid DNA occurs when these DNAs are co-delivered simultaneously and is unlikely to be mediated by cytokine induction. Furthermore, co-transfected plasmids were shown to upregulate transcription, but not translation, of the reporter gene during transient expression. Thus, the observed enhancement may result from competition between co-transfected plasmids and reporter constructs for cellular proteins that interact with transfected DNA, such as histones. Indeed, Pracinostat (SB939), an inhibitor of histone deacetylase, was able to enhance the transient expression of the reporter gene dose-dependently. Overall, this study provides insights that may facilitate improved transient expression of recombinant genes in biotechnological applications.