Meera Singhal

May 5, 2021

5 min read

TALEN Simplified

For over the past decade, zinc finger arrays have been one of the front-runner technologies for gene editing, targeting enzymes, and many other such protein domains (that are specific to a DNA sequence). Through this process, scientists have identified a huge number of zinc finger nucleases hat can recognize various nucleotide triplets. With some trial and error, zinc finger arrays are able to recognize a variety of nucleotide triplets. With years of trial and error, zinc finger arrays are now able to recognize their targets with a high accurate and specificity rate. Fifteen years of research has indicated to scientists that when zinc fingers are fused to a nucleases or activation domain. A zinc finger array is an effective targeting mechanism for molecular tools. Zinc fingers however do have some drawbacks. Not every nucleotide triplet has a corresponding zinc finger, and interactions between zinc fingers within an array can reduce their specificity.

Now, its time for a new form of gene editing to take over. Scientists call it TALEN, or more commonly known as Transcription activator-like effector nucleases. When TALEN was first introduced to the world way back in 2018, the biology field was shaken. Dan Voytas, the cofounder of TALEN and the Professor of Genetics, Cell Biology, and Development at the University of Minnesota. He introduced it to the world during this conference at Stanford. Enough about the background, lets jump into the spicy parts of this article; understanding TALEN, its applications, and a case study surrounding it!

TALEN stands for transcription activator-like effector nucleases. TALEN is another form of gene editing where biologist use a DNA-binding domain to cut and edit specific sequences of DNA. TALEN is another type of artificial nuclease that we can use to cut DNA at very specific recognition sites. These specific recognition enzymes are going to recognize a very specific DNA sequence and cut at that sequence. TALEN is made out of TALEP, which is known as transcription activator-like effector proteins or TAILS. These are proteins that are made from certain bacteria known as Xanthomonas from the Onis bacteremia. TALEP is a type of protein that binds to DNA, well to be more specific, it binds to a specific nucleotide. Since the TALEP can bin to specific nucleotide like adenine or guanine, we can do so much more. To help you visualize this a bit better, imagine if each nucleotide had a little TALE on the end of it- a oval attached to it make a huge weight protein that has hundreds of TALEs attached to it. Each type of nucleotide will have a different type of TALE. We then attach half of an endonuclease’s enzyme like Fok1 (a nuclease that we got from bacteria) to create an active enzyme! TALEN has been taking over the genome editing field for the past three years with its complex but simple nature.

Below, I have listed the top 5 most interesting applications of TALEN since 2020! Just because CRISPR stole the spotlight and fame does not mean TALEN is any less cool!

- Inspired by this article, scientists have used TALEN-based technology/ editing to change the way rice responds to certain proteins. The xa5 gene encodes a basal transcription factor (Tibia) protein with wide spectrum resistance to bacterial blight caused by Xanthomonas Oryza pave. Oryza (Zoo) in rice. It was only found in a few rice ecotypes, and the recessive characteristics limited its application in breeding.

- Inspired by this article, scientists have created a TALEN mediated gene editing technology that is inserted into a mouse model of a Fanconi amenia. The promising ability to genetically modify hematopoietic stem and progenitor cells by precise gene editing remains challenging due to their sensitivity to in vitro manipulations and poor efficiencies of homologous recombination. This study represents the first evidence of implementing a gene editing strategy in a murine safe harbor locus site that phenotypically corrects primary cells from a mouse model of Fanconi anemia A.

- This article inspired scientists to create a TALEN based technology for the genetic improvements of plants. Precise genome editing has been a long-standing goal in the field of biology which has been achieved with the help of engineered nucleases. These engineered nucleases consist of a binding and a nuclease domain which are generally used in the form of a pair. The binding domain binds specifically to a DNA sequence whilst the nuclease domain creates double-strand breaks (DSBs) which are further used for non-homologous end joining or homologous recombination repair.

- Similar to the previous technology, this article inspired scientists to use TALEN and other gene editing tools to edit plant genomes. The highlights of this new technology include;

o Presentation of improvements made on the structure of TALEN.

o Recent approaches are presented for use in crop improvement.

o Novel findings for the application of SSNs to real gene targeting.

o Commercial applications.

- Inspired by this article, scientists have created a TALEN-mediated generation of a knockout rat model. This was inspired by the new find of the NK3 homeobox 1 (NKX3.1) protein. Recently, NKX3.1 was shown to be associated with breast cancer in humans. This method was by the act of finding the prostate weight and fertility was evaluated in the knockout rats, besides determining the proportion of epithelial cells and messenger RNA (mRNA) expression of genes associated with carcinogenesis.

TLDR

- ZFN vs TALEN. In relation to my previous article about ZFNs, we compared the two and the new takeover of TALEN.

- What is TALEN? TALEN is a form of gene targeting. Check out my YouTube Video for a more visual explanation.

Hello! My name is Meera Singhal, and I am a 13-year-old currently fascinated by the field of biotechnology, specifically stem cells and gene editing. I’ve written articles about biotechnology, mindset tips, and a whole variety of up-and-coming topics. Interested? Check out my medium, LinkedIn, YouTube, or TKS Life Portfolio for more content! Curious to see more about me? Consider subscribing to my Newsletter! Thank you so much!