 Crosstalk between histone modifications during the DNA damage response ◦ Histone ◦ Histone modification ◦ DNA damage ◦ DNA damage response

 The componential proteins unit of nucleosome  Histone Octamer ◦ H2A, H2B, H3, H4 ◦ Nature Reviews Cancer 1, (December 2001) | doi: /

 Protein can be modified!  Acetylation, Phosphorylation, Ubiquitination, Mehtylation, Etc  Histone octamer can be also modified Histone is also protein! Nature Reviews Cancer 1, (December 2001) | doi: /

 Double Strand Break(DSB)  Single Strand Break(SSB)  Thymine Dimer by UV

 The most deleterious forms of DNA damage ◦ In most case of SSB, there are templates

 Repair  Death(Apoptosis)  Aging

 Base excision repair(BER)  Nucleotide excision repair(NER)  DSB repair ◦ Homologous recombination(HR) ◦ Non-homologous end-joining(NHEJ)

Peterson C L, Côté J Genes Dev. 2004;18:

 -Ray

 Repair Or Die?  To determine this, Body has to know about DNA damage  How can detect DNA damage? Especially, DSB

H2A variant form 2~25 % population in tissue Conserved motif : SQEY Especially,‘S’ is very critical factor in Damage Response  H2AX is S139 phosphorylated form When DSB occurs,  H2AX appears -> DSB marker

 Doctor : DNA damage response proteins  Amplification of  H2AX  Formation of foci

 MRN complex recognizes DSB site, and binds to DNA end.  And recruits activated ATM  ATM phosphoryates H2AX(it called  H2AX)  NBS1 recruits MDC1 to  H2AX  Amplification of  H2AX Recognition and signal amplification of DNA damage

Michael B. Kastan, Cancer Res 2008;6(4):517–24 ATM also phosphorylates MDC1, 53BP1, BRCA1

 I’m in trouble!  Call doctor! Real Doctor makes holes to reach damaged site How about DNA repair?

 To expose damaged DNA, chromatin must change  -> Loosing!

 Acetylation  Ubiquitination  Methylation

 Generally when acetylated in histone  -> Loosing  And when deacetylated in histone  -> Packing

 TIP60 complex is a kind of HAT ◦ HAT : Histone AcetylTransferase  TIP60 complex acetylates H4 and  H2AX  AcH4 is very critical factor for DDR ◦ Mutation -> Hypersensitive

 Tip49a,b(also known as Rvb1, 2) are involved to TRRAP/Tip60 activity(HAT activity)  Knockdown of Rvb1,2 -> increase of  H2AX Jha S, Mol Cell Biol 2008; 28:

 Why?  AcH4 is important histone to recruit phosphatase  Chromatin Remodeling Factor binds to N-ter of AcH4 and remove  H2AX

 TRRAP/Tip60 relax histone to recruit DNA repair protein effectvely.  Mutation of these proteins -> Reduce recruitment of 53BP1 and Rad51 -> permit to access DNA to open up

 Mono or poly ubiquitin can be signal factor

 UBC13 can interact RNF8 and RNF168 and TIP60 ◦ RNF8 : E3 ligase ◦ RNF168 : E3 ligase ◦ UBC13 : E2 ligase  Nature Reviews Cancer 6, (May 2006)  doi: /nrc1881

 Binds to phosphorylated MDC1 by FHA domain  FHA domain : forkhead associated domain  Ubiquitynate on H2AK63 or H2AXK63  RAP80 can bind to these histones  Abraxas(adaptor protein) binds to RAP80  BRCA1 binds to Abraxas 

 Binds to monoUbH2AX K63  With UBC13, makes polyUbH2AX K63

 TIP60 forms a complex with UBC13 to promote the DNA damage dependent ubiquitylation of Ac  H2AX  Acetylated site is for its ubiquitylation  UBC13 and TIP60 complex is related to histone removal

 H3K79 and H4K20 are important residues  They are methylated in normal, and exposed at DSB  They are docking sites for recruting signal transducer

 53BP1 contains two tandem TUDOR domain  TUDOR domain can bind methylated H3 and H4

 Williams Beuren syndrome factor transcription factor -> Tyrosine kinase  -> phosphorylated T142 of H2AX