크리스퍼, crispr

 

크리스퍼 (CRISPR, Clustered Regularly Interspaced Short Palindromic Repeats) 시스템은 세균 등에서 발견되는 적응 면역 기작으로, 현재는 이를 응용한 유전체 편집 기술인 3세대 유전자 가위(RGENs, RNA-guided engineered nucleases)로 더욱 잘 알려져 있다.

초창기의 크리스퍼는 단순히 DNA를 절단하기 위해 사용되었다. 그 뒤 크리스퍼는 사람 유전체에 완전히 새로운 DNA 절편이나 유전자 전체를 삽입하여 기존의 유전정보를 다른 것으로 바꾸기 위한 기술로 개발하는 과정에 있다. 이러한 기술이 개발된다면 크리스퍼는 유전 질환 외 다른 건강 문제를 치료하는 데에도 널리 사용될 수 있다. 관련기사

종래의 유전체 편집 기법에 비해 월등하게 간편하고 저렴하며, 정확하게 유전체 편집을 가능하게끔 해 '유전공학의 혁명'이라고 불리고 있다. 특히 원하는 유전자를 정확히 찾아내서 이를 쉽게 잘라내는 방식은 생명공학자들에게 새로운 유전자 수술용 메스를 쥐어준 셈이나 마찬가지. 1980년대 분자생물학과 생명공학에 대혁신을 일으킨 유전자 증폭 기술에 맞먹는 대혁신이라고 할 수 있다. 간단한 예로 기존의 연구방법으로는 2년 정도 걸리던 실험을 크리스퍼 시스템을 이용하면 1주일로 단축시킬 수 있다고 한다. 

여기서 크리스퍼(CRISPR)란, 세균의 유전체에서 발견되는 독특한 염기서열로, 'clustered regularly interspaced short palindromic repeats'의 약자이다. '규칙적인 간격을 갖고 나타나는 짧은 회문 구조의 반복 서열'이라는 뜻이다.

 

[발견]

세균의 유전체 내에 크리스퍼 서열이 존재한다는 사실이 1987년 일본 규슈대학의 이시노 요시즈미(石野 良純)박사에 의해 발견되었으나, 당시에는 이 서열이 세균의 어떤 생명 활동에 관여하는 지는 밝혀지지 않은 상태였다. 2007년에 들어서야 이 서열이 세균의 적응면역에 관여한다는 사실이 밝혀졌는데, 이를 밝혀낸 건 놀랍게도 덴마크의 요구르트 회사에서 일하던 과학자들이었다. 

요구르트 배양에 필요한 유산균은 박테리오파지라는 바이러스에 매우 취약해, 유산균 배양조가 파지에 감염되면 유산균들이 떼죽음을 당하기 일쑤였다. 이에 과학자들이 죽은 유산균들 사이에도 꿋꿋이 살아있는 유산균들을 연구한 결과, 유산균이 크리스퍼 시스템을 이용해 파지의 침입에 내성을 갖게 되었다는 사실을 밝혀낸 것이다. 그 원리를 간략하게 설명하면 다음과 같다.

--취득 단계 : 박테리오파지와 같은 바이러스가 세균에 침입하면, 세균은 이들의 DNA 일부를 잘라, 자신의 유전체 중 '크리스퍼 부위(CRISPR loci)', 그 중 반복 서열 사이의 스페이서 부위에 삽입한다.

--발현 단계 : 동일한 바이러스가 다시 침입하면, 세균은 Cas 단백질을 발현함과 동시에, 스페이서와 상보적인 서열의 RNA(crRNA)를 발현한다.
--절단 단계 : crRNA-Cas 복합체가 형성된 상태에서, crRNA가 바이러스 게놈 내 상보적인 서열과 결합하면, Cas 단백질이 바이러스의 DNA를 절단함으로써 바이러스를 죽인다.

고등 생명체에게만 있던 것으로 알려진 적응 면역이 박테리아 단위에도 존재한다는 사실은 놀라운 사실이었지만, 시간이 지나면서 점차 크리스퍼에 대한 관심이 줄어들고 있던 중, 2012년 <사이언스> 지에 제니퍼 다우드나 박사팀이 논문 하나를 발표하였다. 

crRNA의 서열 중 일부를 바꿔주기만 하면, 크리스퍼 시스템을 원하는 DNA 서열을 자르는 '유전자 가위'로 사용할 수 있다는 파격적인 내용의 이 논문이 발표되자마자 크리스퍼 시스템은 유전체 편집 기술로서 엄청난 화제를 불러일으키며, 이를 활용한 다양한 기술들이 개발되기 시작했다. 사르팡티에와 다우드나는 이 업적을 인정받아 2020년 노벨화학상을 수상했다. 업적을 세운 후 노벨상을 받을 때까지 수십 년이 걸리는 게 일반적인데, 논문 발표 후 10년도 채 지나지 않아 수상을 했다는 것은 그 발견이 그만큼 혁신적이었다는 뜻이다.

 

The CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) system is an adaptive immune mechanism found in bacteria, etc., and is now better known as RNA-guided engineered nucleases (RGENs), a genome editing technology that applies them.

Early CRISPR was simply used to cut DNA. CRISPR is then in the process of developing a technology to change existing genetic information into something else by inserting a completely new DNA fragment or the entire gene into the human genome. CRISPR can be widely used to treat health problems other than genetic diseases if these technologies are developed. Related Articles

It is called the 'genetic engineering revolution' because it is far easier and cheaper than conventional dielectric editing techniques, and enables accurate dielectric editing. In particular, the method of accurately identifying the desired gene and cutting it easily is like giving biotechnologists a new gene surgical scalpel. It is a major innovation that is equivalent to the gene amplification technology that revolutionized molecular biology and biotechnology in the 1980s. As a simple example, it is said that an experiment that took about two years with the existing research method can be shortened to one week using the CRISPR system.

CRISPR is a unique sequence found in the genome of a bacterium and stands for "clustered regularly interposed short palindromic repeats." It means "a repetitive sequence of short palindromic structures that appear at regular intervals."



[Found it]

The existence of a CRISPR sequence in the genome of bacteria was discovered in 1987 by Dr. Yoshizumi Ishino of Kyushu University in Japan, but it was not known at the time what kind of life activities the sequence was involved in. It was only in 2007 that it was discovered that the sequence was involved in bacterial adaptive immunity, and surprisingly, it was scientists working for a Danish yogurt company who discovered it.

The lactic acid bacteria required for yogurt culture are very vulnerable to a virus called bacteriophage, and when the lactic acid bacteria culture tank was infected with the phage, the lactic acid bacteria often died in droves. Scientists discovered that lactic acid bacteria used the CRISPR system to become resistant to phage invasion after studying lactic acid bacteria that are still alive even among dead lactic acid bacteria. The principle is as follows.



--Acquisition Step: When a virus such as bacteriophage invades bacteria, the bacteria cut off some of their DNA and insert it into the 'CRISPR loci' of their genome, among them, the spacer site between repetitive sequences.

--Expression Step: When the same virus invades again, the bacteria express the Cas protein and at the same time express RNA (crRNA) of a sequence complementary to the spacer.
--The cleavage step: When the crRNA combines with a complementary sequence within the viral genome, the Cas protein kills the virus by cutting the DNA of the virus.

It was surprising that adaptive immunity, known to have existed only in higher life, also exists in bacterial units, but as interest in CRISPR was gradually decreasing over time, Dr. Jennifer Doudna's team published a paper in the journal Science in 2012.

The CRISPR system sparked a huge buzz as a dielectric editing technology, and various technologies using it began to be developed as soon as this paper, which stated that by altering some of the sequences of the crRNA, the CRISPR system could be used as a 'gene scissors' to cut the desired DNA sequence. In recognition of this achievement, Sarpentier and Daudna were awarded the 2020 Nobel Prize in Chemistry. The fact that the Nobel Prize was won less than 10 years after the publication of the paper indicates that the discovery was as innovative as it is.