Team:Edinburgh UG/Description

Project Description

What is site-specific recombination and why does it matter?

Site-specific recombination (SSR), found mostly in bacteria, viruses and transposons (the so-called parasitic DNA), is one of the many mechanisms which life utilises to perform genetic recombination (Leach, 1996). SSR generally consists of a recombinase protein that mediates recombination, and two DNA elements, called target sites, that are similar or identical to each other that the recombinase recognises (Grindley et al., 2006). Depending on the orientation and the location of the target sites, SSR can perform DNA integration, excision, and exchange. While bacteria use SSR to regulate gene expression and separate two chromosomes during cell division, viruses and transposons use it to mediate chromosomal integration into the bacterial chromosome, hijacking the cellular machinery to replicate themselves.

With the ability to modify DNA in a precise manner, SSR has been used in various fields of research and industrial applications where genetic engineering is required. Click to see the applications of SSR:

Genetic Engineering

a. Conditional Gene Knockout

Site-specific recombinases are highly efficient in excising DNA segments flanked with target sites; this property has been widely adopted by neuroscientists and developmental biologists to perform conditional gene knockout, where a gene can be deleted in specific time and cell types, and is particularly useful to study genes that are essential for development. For example, Hara et al. showed that autophagy was important not only for adaptation to starvation, but also for preventing degeneration of neurons. They demonstrated it by knocking out Atg5, a protein involved in autophagy, specifically in neurons using Cre/LoxP recombination system, as its complete knockout is lethal to the organism. Examples: (1) Hara, T., Nakamura, K., Matsui, M., Yamamoto, A., Nakahara, Y., Suzuki-Migishima, R., Yokoyama, M., Mishima, K., Saito, I., Okano, H., Mizushima, N. (2006) Suppression of autophagy in neural cells causes neurodegenerative disease in mice. Nature. 441: 885-889 (2) Yang, X., Li, C., Herrera, P., Deng, C. (2002) Generation of Smad4/Dpc4 conditional knockout mice. Genesis. 32(2): 80-81

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