View source for Endonuclease

<StructureSection load='' size='350' side='right' scene='49/496318/Cv/1' caption='E. coli EcoRV endonuclease dimer (magenta, green) complex with DNA, (PDB code [[1rva]])'>

== Function ==

'''Endonuclease''' (ENN) cleaves phosphodiester bond within polynucleotide chain.  ENN cleaves DNA at a restriction site which is usually a 6-nucleotide palindrome.  ENN is restriction site–specific.  Various types of ENN differ by their mechanism of action.  ENN is used in genetic engineering to make recombinant DNA.  ENN requires a restriction site and a cleavage pattern.  
*'''ENN-I''' operates on DNA with separate restriction site and cleavage pattern. 
*'''ENN-II''' operates on overlapping restriction site and cleavage pattern.  
*'''ENN-III''' is a bifunctional DNA glycosylase that removes oxidized pyrimidines from DNA<ref>PMID:30959406</ref>.
*'''ENN-IV''' cleaves the DNA backbone 5' of AP sites<ref>PMID:10458614</ref>.
*'''ENN-V''' removes deaminated bases from DNA<ref>PMID:23263163</ref>.
*'''ENN-VII''' recognizes mixmatches in DNA recombinational heteroduplexes and performs their incision<ref>PMID:21237725</ref>.
*'''ENN-VIII''' removes radiolysis thymine products from phage DNA and cleaves the DNA at AP sites<ref>PMID:9405426</ref>.
*'''Structure-specific ENN''' specific for DNA secondary structure rather than for its sequence<ref>PMID:28327556</ref>.
*'''Intron-encoded ENN''' or '''homing ENN''' are encoded by genes with mobile, self-splicing introns. They promote the movement of DNA sequences from one chromosome location to another<ref>PMID:9665136</ref>. <br />
The '''Cas ENN''' proteins are part of '''CRISPR/Cas''' prokaryotic immune system which confers protection from foreign genetic elements like viruses.  The '''CRISPR''' ('''C'''lustered '''R'''egularly '''I'''nterspersed '''S'''hort '''P'''alindromic '''R'''epeats) are DNA loci which are found in ca. 40% of the bacteria.  The CRISPR/Cas system is being used lately as gene editing tool<ref>PMID:20056882</ref>.  For more details see<br />
*[[CRISPR-Cas]]
*CRISPR type I-A (Cascade) - see [[CRISPR subtype I-A]]
*CRISPR type I-B (Cascade) - see [[CRISPR subtype I-B]]
*CRISPR type I-C (Cascade) - see [[CRISPR subtype I-C]]
*CRISPR type I-E (Cascade) - see [[CRISPR type I-E (Cascade)|CRISPR subtype I-E]]
*(CRISPR type I-F (Csy1, Csy2, Csy3) - see [[CRISPR subtype I-F]]
*CRISPR type III-A (Csm complex) - see [[CRISPR subtype III-A (Csm complex)]]
*CRISPR type II-A - see [[CRISPR-Cas9]]
*CRISPR type V (Cpf1, C2c1, C2c3) - see [[CRISPR type V]]
*CRISPR type VI (Cas13a (previously known as C2c2), Cas13b, Cas13c, Cas13d) - see [[CRISPR type VI]]
See also<br />
* [[Apurinic-Apyrimidinic Endonuclease-1]]<br />
* For EcoRV ENN see [[Student Projects for UMass Chemistry 423 Spring 2012-3]]<br />
* For NEI ENN see [[DNA repair protein human endonuclease VIII-like 1 (NEIL1)]].

== Relevance ==

Sickle cell anemia is caused by mutation in the recognition site of MstII ENN.

== Disease ==

Mutation in UV-specific ENN causes Xeroderma pigmentosa. Mutations in tRNA-splicing ENN cause pontocerebellar hypoplasia.

== Structural highlights ==
<scene name='49/496318/Cv/1'>E. coli EcoRV endonuclease dimer with DNA</scene>

<scene name='49/496318/Cv/2'>DNA-protein binding</scene> (PDB code [[1rva]]). 

==3D structures of endonuclease==
[[Endonuclease 3D structures]]

</StructureSection>

== References ==
<references/>


[[Category:Topic Page]]
[[Category:Endonuclease]]