
BRCA1-BARD1 복합체는 DNA 이중 가닥 절단 수리를 위한 DNA 말단 절단을 직접 촉진하며, 동시에 복제 스트레스 하에서 DNA를 보호하는 역할을 한다.


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BRCA1–BARD1 directly promotes double-strand break&nbsp;repair by stimulating long-range DNA end resection pathways.

Mechanism of BRCA1–BARD1 function in DNA end resection and DNA protection - Nature

brca1-bard1-복합체의-dna-말단-절단과-dna-보호-기능-메커니즘


BRCA1-BARD1 복합체의 DNA 말단 절단과 DNA 보호 기능 메커니즘


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FANCD2-FANCI 복합체는 DNA 이중 가닥을 미끄러지며 탐색하다가 단일 가닥-이중 가닥 접합부에서 특이적으로 결합하여 DNA 손상 부위를 인식한다.


FANCD2–FANCI is a sliding clamp that diffuses on double-stranded DNA&nbsp;but stalls when it reaches a single-stranded gap, providing a unified molecular mechanism that reconciles the roles of FANCD2–FANCI in the recognition and protection of stalled replication forks.

FANCD2–FANCI surveys DNA and recognizes double- to single-stranded junctions - Nature

dna-교차결합을-인식하고-단일-가닥-이중-가닥-접합부를-감지하는-fancd2-fanci-복합체


DNA 교차결합을 인식하고 단일 가닥-이중 가닥 접합부를 감지하는 FANCD2-FANCI 복합체



PARP1 응축체는 DNA 수리 단백질의 선별적 분배를 통해 DNA 접합 효율을 향상시킨다.


Poly(ADP-ribose) polymerase 1 (PARP1) is one of the first responders to DNA damage and plays crucial roles in recruiting DNA repair proteins through its activity – poly(ADP-ribosyl)ation (PARylation). The enrichment of DNA repair proteins at sites of DNA damage has been described as the formation of a biomolecular condensate. However, it is not understood how PARP1 and PARylation contribute to the formation and organization of DNA repair condensates. Using recombinant human PARP1 in vitro , we find that PARP1 readily forms viscous biomolecular condensates in a DNA-dependent manner and that this depends on its three zinc finger (ZnF) domains. PARylation enhances PARP1 condensation in a PAR chain-length dependent manner and increases the internal dynamics of PARP1 condensates. DNA and single-strand break repair proteins XRCC1, LigIII, Polβ, and FUS partition in PARP1 condensates, although in different patterns. While Polβ and FUS are both homogeneously mixed within PARP1 condensates, FUS enrichment is greatly enhanced upon PARylation whereas Polβ partitioning is not. XRCC1 and LigIII display an inhomogeneous organization within PARP1 condensates; their enrichment in these multiphase condensates is enhanced by PARylation. Functionally, PARP1 condensates concentrate short DNA fragments and facilitate compaction of long DNA and bridge DNA ends. Furthermore, the presence of PARP1 condensates significantly promotes DNA ligation upon PARylation. These findings provide insight into how PARP1 condensation and PARylation regulate the assembly and biochemical activities in DNA repair foci, which may inform on how PARPs function in other PAR-driven condensates.

### Competing Interest Statement

The authors have declared no competing interest.

PARP1 condensates differentially partition DNA repair proteins and enhance DNA ligation

parp1-응축체가-dna-수리-단백질을-선별적으로-분배하고-dna-접합을-향상시킨다


PARP1 응축체가 DNA 수리 단백질을 선별적으로 분배하고 DNA 접합을 향상시킨다



대장균에서 RecBCD 발현은 Hfq 단백질에 의한 전사 후 조절을 통해 최적의 수준으로 유지된다.


All living organisms have developed strategies to respond to chromosomal damage and preserve genome integrity. One such response is the repair of DNA double-strand breaks (DSBs), one of the most toxic forms of DNA lesions. In Escherichia coli , DSBs are repaired via RecBCD-dependent homologous recombination. RecBCD is essential for accurate chromosome maintenance, but its over-expression can lead to reduced DNA repair ability. This apparent paradox suggests that RecBCD copy numbers may need to be tightly controlled within an optimal range. Using single-molecule fluorescence mi-croscopy, we have established that RecB is present in very low abundance at mRNA and protein levels. RecB transcription shows high fluctuations, yet cell-to-cell protein variability remains remarkably low. Here, we show that the post-transcriptional regulator Hfq binds to recB mRNA and down-regulates RecB protein translation in vivo . Furthermore, specific disruption of the Hfq-binding site leads to more efficient translation of recB mRNAs. In addition, we observe a less effective reduction of RecB protein fluctuations in the absence of Hfq. This fine-tuning Hfq-mediated mechanism might have the underlying physiological function of maintaining RecB protein levels within an optimal range.

### Competing Interest Statement

The authors have declared no competing interest.

An Hfq-dependent post-transcriptional mechanism fine tunes RecB expression in Escherichia coli

대장균의-recbcd-발현-미세조정은-최적의-dna-수리를-위해-필요한-전사-후-조절


대장균의 RecBCD 발현 미세조정은 최적의 DNA 수리를 위해 필요한 전사 후 조절



타디그라드는 이온화 방사선에 대한 탁월한 저항성을 보이며, 이는 DNA 수리 기작이 주요한 역할을 하는 것으로 나타났다. 특히 TDR1이라는 새로운 타디그라드 특이적 DNA 결합 단백질이 이온화 방사선에 의한 DNA 손상 대응에 관여하는 것으로 확인되었다.


Tardigrades, microscopic animals found in virtually all ecosystems, are renowned for their remarkable ability to withstand extreme conditions. Recent studies have identified novel tardigrade specific protein families that aid in resistance to desiccation and ionizing radiation (IR). Notably, a tardigrade specific DNA binding protein called Dsup (for DNA damage suppressor) has been found to protect from X-ray damage in human cells and from hydroxyl radicals in vitro . However, Dsup has only been found in two species within the Hypsibioidea superfamily.

To better understand mechanisms underlying radio-resistance in the Tardigrada phylum, we first characterized DNA damage and repair in response to IR in the model species Hypsibius exemplaris . By analysis of phosphorylated H2AX, we demonstrated the induction and repair of DNA double-strand breaks after IR exposure. Importantly, the rate of single-strand breaks induced was roughly equivalent to that in human cells, suggesting that DNA repair plays a predominant role in the remarkable radio-resistance of tardigrades. In order to identify novel tardigrade specific genes involved, we next conducted a comparative transcriptomics across three species, H. exemplaris , Acutuncus antarcticus and Paramacrobiotus fairbanksi , the latter belonging to the Macrobiotoidea superfamily known to lack Dsup homologs. In all three species, many genes of DNA repair were among the most strongly overexpressed genes alongside a novel tardigrade specific gene, named T ardigrade D NA damage R esponse protein 1 (TDR1). We found that TDR1 protein interacts with DNA and forms aggregates at high concentration suggesting it may condensate DNA and act by preserving chromosome organization until DNA repair is accomplished. Remarkably, when expressed in human cells, TDR1 improved resistance to Bleomycin, a radiomimetic drug. Based on these findings, we propose that TDR1 is a novel tardigrade specific gene responsible for conferring resistance to IR. Our study sheds light on mechanisms of DNA repair helping to cope with high levels of DNA damage. Furthermore, it suggests that at least two tardigrade specific genes, respectively for Dsup and TDR1, have independently evolved DNA-binding functions that contribute to radio-resistance in the Tardigrada phylum.

### Competing Interest Statement

The authors have declared no competing interest.

Comparative transcriptomics reveal a novel tardigrade specific DNA binding protein induced in response to ionizing radiation

이온화-방사선에-대한-타디그라드-특이적-dna-결합-단백질의-발현-증가


이온화 방사선에 대한 타디그라드 특이적 DNA 결합 단백질의 발현 증가
