The light-controlled switching system is composed of several related parts, transcription activator (TALE), CRY2 (a light-sensitive protein) and CIB1 (the natural binding protein of CRY2). The DNA binding protein TALE synthesizes a specific form to bind to DNA. TALE merges with CRY2. When CRY2 encounters light, it will change structure and combine with CIB1. These parts work synergistically to exercise the genetic command of the cell-to regulate the transcription of DNA into mRNA.
Using this principle, the researchers transformed CIB1 into a form that can be combined with another protein to participate in the regulation of gene expression. After the optical switch system enters the cell, TALE binds to the target DNA. When light is irradiated to the cell, CRY2 protein binds to CIB1 which was originally free in the cell. The gene activation protein carried by CIB1 initiates DNA replication or transcription. Alternatively, the gene suppressor protein carried by CIB1 inhibits DNA replication or transcription.
A single light pulse is sufficient to induce protein binding and initiate DNA replication and transcription. The researchers found that light pulses about once per minute are the most effective frequency for continuous transcription. In addition, with continuous 30-minute light pulses, the mRNA level of the target gene transcribed significantly increased, and once the light pulses stopped, the mRNA level began to decline within about 30 minutes.
The researchers studied 30 different genes in neurons and animal-derived cells from the laboratory and found that the gene switching system can increase their transcription levels.
Karl Deisseroth, a professor of bioengineering and optogenetics at Stanford University, said the innovation of the study is that its light-controlled switch system controls not synthetic genes but genes taken from cells. Based on this technology, you can observe the expression of specific genes at specific time points.
Epigenetic modification
Another role of gene expression regulation switches is to study epigenetic modifications. An important field of epigenetics is the chemical modification of histones. Histones can be combined with DNA to control the expression of related genes. The researchers discovered that epigenetic modifications can be altered through TALE fusion with histones.
Epigenetic modification plays an important role in the process of learning and memory formation, but due to the lack of effective ways to intervene in the modification of histones, this subject has not been further studied. The application of new technologies can precisely intervene in the expression of a single gene, thus providing the possibility of research on this subject.
At present, researchers have confirmed that some histone domains can be combined with light-sensitive proteins, and they are expanding the types of histone modifications that can be applied to gene regulatory systems.
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