SPOC1 modulates DNA repair by regulating key determinants of chromatin compaction and DNA damage response
Authors: Sarah Kinkley
Lauriane Fritsch
Andreas Mund
Malte Kriegs
Anne-Sophie Hoffbeck
Slimane Ait-Si-Ali
Kerstin Reumann
Hans Will
Evi Soutoglou
Hannah Staege
Valentine Battisti
Tobias Schubert
Journal: Nucleic Acids Research (2012)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: SPOC1; DNA double-strand breaks; repair foci; ionizing radiation-induced foci; non-homologous end-joining
Affiliations: Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Department of General Virology, Martinistrasse 52, 20251 Hamburg, Germany.

Abstract:  Survival time-associated plant homeodomain (PHD) finger protein in Ovarian Cancer 1 (SPOC1, also known as PHF13) is known to modulate chromatin structure and is essential for testicular stem-cell differentiation. Here we show that SPOC1 is recruited to DNA double-strand breaks (DSBs) in an ATM-dependent manner. Moreover, SPOC1 localizes at endogenous repair foci, including OPT domains and accumulates at large DSB repair foci characteristic for delayed repair at heterochromatic sites. SPOC1 depletion enhances the kinetics of ionizing radiation-induced foci (IRIF) formation after γ-irradiation (γ-IR), non-homologous end-joining (NHEJ) repair activity, and cellular radioresistance, but impairs homologous recombination (HR) repair. Conversely, SPOC1 overexpression delays IRIF formation and γH2AX expansion, reduces NHEJ repair activity and enhances cellular radiosensitivity. SPOC1 mediates dose-dependent changes in chromatin association of DNA compaction factors KAP-1, HP1-α and H3K9 methyltransferases (KMT) GLP, G9A and SETDB1. In addition, SPOC1 interacts with KAP-1 and H3K9 KMTs, inhibits KAP-1 phosphorylation and enhances H3K9 trimethylation. These findings provide the first evidence for a function of SPOC1 in DNA damage response (DDR) and repair. SPOC1 acts as a modulator of repair kinetics and choice of pathways. This involves its dose-dependent effects on DNA damage sensors, repair mediators and key regulators of chromatin structure. 

Retracted: No

PubPeer comments:
 Figure 6 continued. Much more similar than expected. https: imgur.com oIkVtNN , 
 Dear Oligarrhena Micrantha, Thanks for raising this concern. Indeed, there should be a blank with a u00b4no detectableu00b4 signal label. In the SOLUBLE fractions (under conditions used in this study -150 mM NaCl, 50 mM HEPES, 0.1% NP-40) no detectable signal was present for histone(s) H3, H3K9me3 and histone binding proteins HP1-alpha, beta and gamma. No manipulation of the data in any way were made. We apologize to our readers for any confusion this might have caused. , 
 #2 I think what is being pointed out is not that they are blank, but that the noise in the highlighted blanks is surprisingly similar. Please take a closer look. , 
 I agree. This is indeed confusing. There should be a blank and label saying - no detectable signal, instead of (similar) noise. This is very unfortunate and we apologize to our readers for any confusion this might have caused. , 
 Hopefully you can appreciate that in panel B the same subcellular fractionation was also performed in CV1. The same antibodies (H3, HP1-alpha, and HP1-beta) like in panel A were used. The histone and the histone binding proteins are exclusively found, under these conditions, in the chromatin fraction. In panel B, all 8 samples were loaded side by side on the same gel as clearly visible. For this reason, the displayed similar noise in panel a does not alter the conclusions of our study or the hypothesis we proposed. However, this is very unfortunate and we apologize to our readers for any confusion this might have caused and are in contact with the journal for clarification. , 
 Dear Dr. Mund, Would you happen to have the original images for the colony forming assays? It may just be coincidence, of course, but the backgrounds for the plates (but not the well contents) have uncanny similarities in places. I have tried to use contrast adjustment to demonstrate what I mean in the images below, but it is hard to match the exact same contrast. Add to this the image compression and image noise. However, I hope I am able to get across my concerns below. Fig 5b ![file] Fig 5d (I added a few boxes to direct the eye to some details that reoccur in an improbable fashion.) ![file] , 
 Yes, I have the original images and I am happy to share them with you. The images were taken with an ordinary scanner. I think the confusion comes from the way the images were scanned. The similar background comes from e.g. micro scratches on the glass plate. I will post the original files for figure 5B for illustration, but I am happy to share the rest if still needed. I hope you will get across your concerns now! ![file] ![file] , 
 Regarding the comment on figure 6. We have reviewed now the original western blots. Unfortunatly, there was a mistake during the image processing that has been corrected now. The result is the same and does not change the conclusion of the western blot analysis. We are in contact with the journal. We thank you for bringing this up. ![file] , 
 #7 Thank you, Dr. Mund, for alleviating my concerns. , 
 Published: 05 September 2020 Corrigendum Nucleic Acids Research,2012, 40(22): 11363u201311379, https: doi.org 10.1093 nar gks868 The authors would like to apologize for a mistake made during the construction of Figure 6. The HP1-u03b2, HP1-u03b3, and H3 negative western blot results of the soluble-rich fraction were accidental masked with the same noise background. This error happened during figure arrangement. A new Figure 6 where the noise background has been removed, revealing the original negative data behind it, is provided below. This error does not change the conclusion of the western blot analysis nor the scientific conclusion of the article. ![file] ,