Construction of artificial promoters sensitively responsive to sonication in vitro

A Simple Method for Constructing Artificial Promoters Activated in Response to Ultrasound Stimulation

It has been pointed out that ultrasound could be used as a controller for bioprocesses including gene expression since its energy can noninvasively reach deep in the body. Gene expression may be timely and spatially controlled by ultrasound, thus providing necessary bioactive proteins for the targeted tissue in a timely fashion. Although there are many processes involved in gene expression control, one of the most important processes is transcription, and the promoter plays an essential role in it. There are several promoters known to be activated in response to ultrasound irradiation . However, in our opinion, an artificial promoter is more suitable for clinical use. We herein describe simple methods to construct promoters that are responsive to ultrasound irradiation by randomly combining cis-elements (transcription factor binding motifs) and thereby improve its reactivity to ultrasound irradiation .

Precision control of recombinant gene transcription for CHO cell synthetic biology

The next generation of mammalian cell factories for biopharmaceutical production will be genetically engineered to possess both generic and product-specific manufacturing capabilities that may not exist naturally. Introduction of entirely new combinations of synthetic functions (e.g. novel metabolic or stress-response pathways), and retro-engineering of existing functional cell modules will drive disruptive change in cellular manufacturing performance. However, before we can apply the core concepts underpinning synthetic biology (design, build, test) to CHO cell engineering we must first develop practical and robust enabling technologies. Fundamentally, we will require the ability to precisely control the relative stoichiometry of numerous functional components we simultaneously introduce into the host cell factory. In this review we discuss how this can be achieved by design of engineered promoters that enable concerted control of recombinant gene transcription. We describe the specific mechanisms of transcriptional regulation that affect promoter function during bioproduction processes, and detail the highly-specific promoter design criteria that are required in the context of CHO cell engineering. The relative applicability of diverse promoter development strategies are discussed, including re-engineering of natural sequences, design of synthetic transcription factor-based systems, and construction of synthetic promoters. This review highlights the potential of promoter engineering to achieve precision transcriptional control for CHO cell synthetic biology.

Regulation of gene expression in human prostate cancer cells with artificially constructed promoters that are activated in response to ultrasound stimulation

We chose promoters responsive to sonication in LNCap cells, a prostate cancer cell line, out of a library composed of DNA fragments constructed by linking the TATA box sequence to randomly combined cis-acting elements of transcription factors activated in response to radiation in prostate cancer cells. When a plasmid containing the luciferase gene under control of a promoter was transfected into LNCap cells and sonicated with 1 MHz ultrasound at 0.5 W/cm(2), 10% DF for 60s, 13 promoters showed more than 10-fold enhancement compared with their counterparts without sonication 12h after sonication. As to their responsiveness to sonication, the best two promoters were then compared to clone 880-8, a derivative from clone 880 that was created by random introduction of point mutations and was shown to have an improved response to X-ray irradiation. We then took clone 880-8 for further analyses since it showed the highest enhancement to sonication, though not statistically significant from the others. Next, we employed a retrovirus vector and stably introduced the luciferase gene under control of clone 880-8 into LNCap cells to establish a cell line. When the cell line was sonicated with 1 MHz ultrasound at 0.5 W/cm(2), 10% DF for 60s, luciferase expression was enhanced up to 14.8-fold 12h after sonication. We then established another cell line by replacing the luciferase gene with the fcy::fur gene, a suicide gene, and when the cell line was sonicated with 1 MHz ultrasound at 0.5 W/cm(2), 10% DF for 60s, expression of the gene was enhanced, showing the maximum expression 12-24h after sonication. When the cells were incubated in medium containing 5-fluorocytosine, cell survival ratio decreased dose dependently with 5-fluorocytosine only after sonication treatment, suggesting this promoter could be utilized for gene expression control with ultrasound.

Ultrasound stimulation induces microRNA expression changes that could be involved in sonication-induced apoptosis

PURPOSE

The purpose of this study is to investigate the involvement of microRNAs (miRNAs) in sonication-induced apoptosis.

METHODS

U937 cells derived from human leukemia were sonicated with 1-MHz ultrasound at 0.4 W/cm(2) and 10 % duty factor for 60 s, a condition inducing apoptosis. The total RNA was extracted from cells at various timings after sonication and subjected to microarray and real-time PCR for miRNA expression analyses.

RESULTS

Expression of several miRNAs was significantly affected by sonication. For miR-424* and miR-720, whose expressions were eminently decreased by sonication, cell lines overexpressing these miRNAs were established. Conversely, for miR-663B and miR-663, whose expressions were eminently increased by sonication, cell lines inhibiting these miRNA functions were established. When these cell lines were sonicated, a cell line inhibiting miR-663B function significantly increased sonication-induced apoptosis, suggesting this may be involved in cellular responses to sonication. Two genes that could induce apoptosis, KSR2 and CREBZF, were identified as potential target genes of miR-663B since potential target sequences on their 3' UTR mediated to decrease expression of a reporter gene.

CONCLUSION

These results suggest that miRNAs may be involved in cellular responses to ultrasound through their expression changes caused by sonication.

Development of a therapeutically important radiation induced promoter

Radio-genetic therapy is a combination of radiation therapy and gene therapy that may solve some of the problems associated with conventional radiotherapy. A promoter responsive to radiation was obtained from a promoter library composed of DNA fragments created by linking the TATA box signal to randomly combined binding sequences of transcription factors that are reactive to radiation. Each promoter connected to the luciferase gene, was evaluated by luciferase expression enhancement in transfected cells after X-ray irradiation. The reactivity of the best promoter was improved by the random introduction of point mutations and the resultant promoter showed more than a 20-fold enhancement of the luciferase expression after X-ray irradiation at 10 Gy. The expression of downstream genes was also enhanced in stably transfected cells not only by X-rays but also by proton beam irradiation; and either enhancement was attenuated when an anti-oxidant was added, thus suggesting the involvement of oxidative stress in the promoter activation. Constructed promoters were also activated in tumors grown in mice. In addition, cell killing with the fcy::fur gene (a suicide gene converting 5-fluorocytosin to highly toxic 5-fluorouracil) increased dose-dependently with 5-fluorocytosin only after X-ray irradiation in vitro. These results suggest that promoters obtained through this method could be used for possible clinical applications.

Perspectives on synthetic promoters for biocatalysis and biotransformation

Acting on the transcriptional level, synthetic promoters have been useful tools for controlling gene expression and have applications in many fields. Here, we discuss synthetic promoters and libraries in regard to current and future applications in the field of biocatalysis or biotransformation. We also focus on synthetic promoter design principles and distinguish between prokaryotic and eukaryotic destinations. The natural toolboxes available for tuneable gene expression and the regulation of enzyme function are limited and primarily host specific. Synthetic biology offers generally applicable concepts and quick implementation. Smart alternatives to transcriptional regulation enrich the engineer's tool box for optimizing industrial enzyme production and host-cell physiology for whole-cell processes. Industrially applicable, tuneable enzyme cascades and artificial circuits for iterative up- and down-regulation will soon be achieved.