How Does DNA Template Length Influence Gene Expression in Cell Free Systems?

3D sketch of coupled transcription/translation in a cell free system. A recent paper looks at the effect of DNA Template Length  on gene expression.

Cell-free gene expression systems are a staple tool for the researcher seeking to understand the regulation of transcription and translation. Many factors can affect the efficiency of cell-free gene expression including vector sequence, reaction components and the template DNA concentration. One factor that has not been extensively studied is how DNA template length influences gene expression.

Continue reading “How Does DNA Template Length Influence Gene Expression in Cell Free Systems?”

Cell Free Expression Application: In vitro degradation assay

A protein chain being produced from a ribosome.
A protein chain being produced from a ribosome.

Researchers and clinicians are fairly certain that all cervical cancers are caused by Human Papillomavirus (HPV) infections, and that HPV16 and HPV18 are responsible for about 70% of all cases. HPV16 and HPV18 have also been shown to cause almost half the vaginal, vulvar, and penile cancers, while about 85% of anal cancers are also caused by HPV16.

E6 is a potent oncogene of HR-HPVs, and its role in progression to malignancy continues to be explored. The E6 oncoprotein of HPV can promote viral DNA replication through several pathways. It forms a complex with human E3-ubiquitin ligase E6-associated protein (E6AP), which can in turn target the p53 tumor-suppressor protein, leading to its ubiquitin-mediated degradation. In particular, E6 from HR-HPVs can block apoptosis, activate telomerase, disrupt cell adhesion, polarity and epithelial differentiation, alter transcription and G-protein signaling, and reduce immune recognition of HPV-infected cells.

In a recent publication a new procedure generated a stable, unmutated HPV16 E6 protein (1). Continue reading “Cell Free Expression Application: In vitro degradation assay”

Cell-Free Kinase Assays

Protein phosphorylation is one of the most biologically relevant modifications and is involved in many eukaryotic and prokaryotic cellular signaling processes. It is estimated that one-third of human proteins are phosphorylated.

The following examples utilize the ability of cell free experession to express active proteins, and when supplemented with the necessary components (e.g., ATP, NaCl), to be used for the characterization of phosphorylation events.

Modrof, J. et al. (2005) Phosphorylation of bluetongue virus nonstructural protein 2 is essential for formation of viral inclusion bodies. J. Vir. 79, 10023–31. Use of TNT® cell-free to express NS2 and NS2 mutant proteins for use in vitro kinase assays to confirm phosphorylation by protein kinase CK2.

Kwon, S. et al. (2005) Signal pathway of hypoxia-inducible factor-1alpha phosphorylation and its interaction with von Hippel-Lindau tumor suppressor protein during ischemia in MiaPaCa-2 pancreatic cancer cells. Clin. Cancer Res. 11, 7607–13. The TNT® system was used to identify which p38 mitogen-activated protein kinase isoform(s) was cabable of phosphorylation of HIF—1 alpha

Harris, J. et al. (2006). Nuclear accumulation of cRel following C-terminal phosphorylation by TBK1/IKK epsilon. J. Immunol. 177, 2527–35. IKK and IKK mutants were expressed using TNT and used in a vitro kinase assay to characterize the recognition motif in cRel transcription domain

Jailais, Y. et al. (2011) Tyrosine phosphorylation controls brassinosteroid receptor activation by triggering membrane release of its kinase inhibitor. Genes Dev. 25, 232–37. Using a vitro kinase assay, full–length and truncations versions of the Brassinostediod-insentive receptor protein were expressed using the TNT® system and incubated with purified BR11 kinase domain to determine binding sites of the two proteins.