Researchers release genetic engineering standardization components

Funded by the National Science Foundation, BIOFAB was established in California in 2009 to establish standardized DNA sequence elements to better control gene expression and advance the development of synthetic biology. Using these standardized DNA sequences, biologists can simply engineer a variety of genes to create specialized cells that produce drugs or perform other tasks.

BIOFAB is like a special factory that specializes in the development of DNA tools for genetic engineering. A few days ago, BIOFAB launched their *batch product, a DNA sequence element that precisely controls gene expression in E. coli.

It has been found that even in fairly mature expression systems (such as E. coli), the expression of the inserted gene does not necessarily meet expectations, which is a key obstacle to synthetic biology.

Gene expression includes RNA transcription and protein translation. To express a gene of interest in a cell, it is necessary to add some recognition sequences upstream. For example, a synthetic RNA transcript requires a promoter sequence, while protein translation requires a ribosome binding site RBS. Over the past three decades, scientists have accumulated a large number of these sequences and used them to express genes of interest. However, some sequences are strong and some are weak, resulting in unstable levels of RNA and protein synthesis.

Drew Endy and Adam Arkin of BIOFAB published two articles in this week's issue of Nature Methods , pointing out that the effects of these DNA elements are difficult to predict. They led the researchers to combine a number of different promoter-RBS sequences into a gene encoding a fluorescent protein and then detect the level of protein synthesis. Studies have shown that the genes that follow are different, and the effects of each combination are quite different.

The article also cited a previous finding that scientists who wish to express proteins at specific levels actually have a 50% chance of achieving the desired yield. The randomness of this gene expression is a major challenge for synthetic biologists because they often need to establish systems for multi-gene expression.

To this end, the BIOFAB research team designed a promoter and RBS sequence for E. coli that does not interfere with downstream DNA. The effects of these components are independent of the target gene, which helps scientists control gene expression more rigorously. Studies have shown that the use of these components greatly increases the probability of gene expression levels (about 93%). Now, researchers can get these sequences for free through the Internet, and some of Arkin's colleagues have begun to benefit from it.

In addition, the researchers designed a statistical method to measure the performance variability of promoter and RBS sequences. This method is also applicable to other genetic elements in synthetic biology. On this basis, scientists can establish specifications for each component to make their research and results sharing more convenient.