53BP1 and BRCA1 control pathway choice for stalled replication restart

Abstract

The cellular pathways that restart stalled replication forks are essential for genome stability and tumor prevention. However, how many of these pathways exist in cells and how these pathways are selectively activated remain unclear. Here, we describe two major fork restart pathways, and demonstrate that their selection is governed by 53BP1 and BRCA1, which are known to control the pathway choice to repair double-strand DNA breaks (DSBs). Specifically, 53BP1 promotes a fork cleavage-free pathway, whereas BRCA1 facilitates a break-induced replication (BIR) pathway coupled with SLX-MUS complex-mediated fork cleavage. The defect in the first pathway, but not DSB repair, in a 53BP1 mutant is largely corrected by disrupting BRCA1, and vice versa. Moreover, PLK1 temporally regulates the switch of these two pathways through enhancing the assembly of the SLX-MUS complex. Our results reveal two distinct fork restart pathways, which are antagonistically controlled by 53BP1 and BRCA1 in a DSB repair-independent manner.

Non-enzymatic roles of human RAD51 at stalled replication forks

“…Further, our results indicate that the RAD51-dependent, strand exchange-dependent mechanism is more predominant after 8 hours of exposure to HU as compared to 5 hours of exposure, while the converse is true for the RAD51-dependent, strand exchange-independent mechanism. These data are consistent with a previous study that identified an early, cleavageindependent restart pathway involving 53BP1 and a late, HR-dependent pathway involving BRCA1 48 .…”

“…This observation suggests that replication fork remodeling mediated by hsRAD51-II3A traps replication restart intermediates that cannot be resolved by RAD51 strand exchange-independent pathways. The partial dependency of 53BP1 foci on MUS81 suggests that a major fraction of the trapped intermediates are collapsed forks, but it is possible that the processing of unbroken reversed forks is also blocked by RAD51-II3A, given prior evidence that 53BP1 can localize to replication forks prior to DSB formation 44,48 .…”

“…In addition to being recruited at broken DNA ends formed by fork collapse, 53BP1 may form foci at DNA ends of reversed forks (i.e. the "middle toe" of the chicken foot) 44 , and is recruited to stalled forks early in the replication response 48 . As a means of determining if the observed 53BP1 foci that accumulate in RAD51-II3A expressing cells were due to fork collapse mediated by MUS81, we asked if the observed accumulation could be reduced or eliminated by siMUS81 ( Figure 5, Supplemental Figure 3).…”

Identification of regulators of poly-ADP-ribose polymerase (PARP) inhibitor response through complementary CRISPR knockout and activation screens

“…25,26 However, 53BP1 has been implicated in additional PARPi-relevant contexts, such as at the replication fork. [38][39][40] The finding that REV7 is also required for the resistance caused by TIP60 depletion supports a mechanism involving activity at the double-strand break; 41 however, other potential roles for REV7 at the replication fork have not yet been thoroughly characterized. 42 Therefore, other function(s) of 53BP1/REV7 may potentially be involved in the rescue of PARPi-induced cytotoxicity downstream of TIP60 depletion in BRCA2-deficient cells.…”

Sparse signal recovery for localization of coherent far- and near-field signals

“…(9)'daki ζ ifadesi, l 1 /l 2 -kaideleri arasındaki ödünleşime karşılık gelmektedir [16]. Eger ζ çok büyük ise l 1 -kaideli ifadeyi vurgulamaktadır.…”