Maintaining Genome Integrity: Actin Polymerization Stabilizes Chromatin Bridges in Cytokinesis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors 1. This article reviews the role of chromatin bridges and the mechanism by which cells prevent the breakage of chromatin bridges, which is beneficial for readers to understand the role and mechanism of chromatin bridges. To enhance the readability of this article, it is suggested that the author reorganize the structure of the article and add subheadings to each part.   2. Lines 47-49 mention that chromosomal fragmentation might be a key event in the occurrence of cancer. But what proportion of such chromosomal fragmentation is caused by abnormal chromatin bridges? That is to say, what is the direct evidence of the relationship between chromatin bridge abnormalities and the occurrence of cancer? 3. There are two mechanisms for stabilizing chromatin bridges in human cells. It would be best to explain this mechanism using a graphical approach, with both text and images, to make it easier for readers to understand. 4. The author should not confuse the concepts of DNA bridges and chromatin bridges. 5. The ANKLE1 enzyme prevents the formation of DNA fragments and micronuclei caused by mechanical breakage by specifically cutting chromatin bridges, maintaining genomic stability. Please compare the similarities and differences between the formation of actin plaques and the action of ANKLE1 enzyme.

Author Response

Point by point response

Reviewer 1

1. This article reviews the role of chromatin bridges and the mechanism by which cells prevent the breakage of chromatin bridges, which is beneficial for readers to understand the role and mechanism of chromatin bridges. To enhance the readability of this article, it is suggested that the author reorganize the structure of the article and add subheadings to each part.  

 

We thank the reviewer for the constructive comments. We have now added subheadings to each part.

 

2. Lines 47-49 mention that chromosomal fragmentation might be a key event in the occurrence of cancer. But what proportion of such chromosomal fragmentation is caused by abnormal chromatin bridges? That is to say, what is the direct evidence of the relationship between chromatin bridge abnormalities and the occurrence of cancer?

We thank the reviewer for the comments. In cell culture, approximately 30-50% of chromatin bridges resolve after, several hours, presumably from a combination of reasons raising from DNA decatenation to chromatin breakage as the daughter cells move apart, to the specific function of nucleases such as ANKLE1 (Umbreit et al., 2020) (Jiang et al., 2025) (Petsalaki and Zachos, 2019). Although there is no direct evidence that chromatin bridges cause cancer, a crucial relationship between chromatin bridges and chromothripsis has been established (Umbreit et al., 2020) and chromothripsis has been associated with cancer (Cai et al., 2014; Cortes-Ciriano et al., 2020; Kim et al., 2013; Kloosterman et al., 2011).

 

3. There are two mechanisms for stabilizing chromatin bridges in human cells. It would be best to explain this mechanism using a graphical approach, with both text and images, to make it easier for readers to understand.

We thank the reviewer for the suggestion. We have now added a new Figure (Figure 1) describing the activation of the abscission checkpoint in cytokinesis with chromatin bridges.

 

 

4. The author should not confuse the concepts of DNA bridges and chromatin bridges.

We replaced the words DNA bridges with chromatin bridges throughout the manuscript.

 

5. The ANKLE1 enzyme prevents the formation of DNA fragments and micronuclei caused by mechanical breakage by specifically cutting chromatin bridges, maintaining genomic stability. Please compare the similarities and differences between the formation of actin plaques and the action of ANKLE1 enzyme.

 

ANKLE1 processes chromatin bridges but we don’t know yet if these bridges contain actin patches. It is a very interesting question for future investigation. One similarity between chromatin bridges resolved by ANKLE1 and chromatin bridges that form actin patches is that both mechanisms act in the presence of DNA tension. There isn’t a known correlation of actin patch formation with the role of ANKLE1 in chromatin bridge resolution.

We added the following sentences:

Do chromatin bridges that are processed by the endonuclease ANKLE1 form actin patches or ANKLE1 cuts chromatin bridges in a controlled way in the absence of actin patches?

 

Reviewer 2 Report

Comments and Suggestions for Authors

Sofia Balafouti and colleagues present a review-like perspective article focusing on recent work from their laboratory on the close relationship of actin and chromatin. In general, the article is comprehensibly written and highlights interesting observations while also discussing other scientific implications in this particular field, it would however benefit from some compacting of the first two chapters. In addition, in my opinion, higher quality figures would much further highlight the importance of the reviewed work and expand the potential audience.

Author Response

Reviewer 2

Sofia Balafouti and colleagues present a review-like perspective article focusing on recent work from their laboratory on the close relationship of actin and chromatin. In general, the article is comprehensibly written and highlights interesting observations while also discussing other scientific implications in this particular field, it would however benefit from some compacting of the first two chapters. In addition, in my opinion, higher quality figures would much further highlight the importance of the reviewed work and expand the potential audience.

We thank Reviewer 2 for the comments. We added more subheadings for easier reading. We also added Figure 1 in order to highlight the two mechanisms for stabilizing chromatin bridges.