Abstract
p50, the mature product of NFKB1, is constitutively produced from its precursor, p105. Here, we identify BARD1 as a p50-interacting factor. p50 directly associates with the BARD1 BRCT domains via a C-terminal phospho-serine motif. This interaction is induced by ATR and results in mono-ubiquitination of p50 by the BARD1/BRCA1 complex. During the cell cycle, p50 is mono-ubiquitinated in S phase and loss of this post-translational modification increases S phase progression and chromosomal breakage. Genome-wide studies reveal a substantial decrease in p50 chromatin enrichment in S phase and Cycln E is identified as a factor regulated by p50 during the G1 to S transition. Functionally, interaction with BARD1 promotes p50 protein stability and consistent with this, in human cancer specimens, low nuclear BARD1 protein strongly correlates with low nuclear p50. These data indicate that p50 mono-ubiquitination by BARD1/BRCA1 during the cell cycle regulates S phase progression to maintain genome integrity.
Highlights
P50, the mature product of NFKB1, is constitutively produced from its precursor, p105
Mounting evidence suggests that the mature product of NFKB1, p50, promotes genome stability and tumor suppression
To elucidate the mechanism by which p50 acts in this manner, we used affinity purification coupled with MS/MS and identified BRCA1-associated RING domain-1 (BARD1) as a p50-interacting factor. p50 directly associated with the BARD1 BRCT domains independent of BRCA1
Summary
P50 interacts with BARD1 BRCT domains in response to ATR. Phosphorylation of p50 S329 (referred to here as S328 based on UniProt isoform 1: P19838-1) was previously shown to be required for genome stability[13]. Treatment with TAM resulted in decreased p50 enrichment at over 40 % of these sites (Fig. 5k), a finding consistent with the lower DNA binding of p50S337D relative to p50wt on gel shift Together, these data indicate that the ATR-induced interaction of p50 with BARD1 promotes p50 stabilization and nuclear export and that activation of ATR results in a general decrease in p50 chromatin enrichment. Covalent addition of a single ubiquitin to p502KR significantly reduced both the percentage of cells in S-phase and overall cellular proliferation relative to parental p502KR and almost to the level seen with p50wt (Fig. 6h and Supplementary Fig. 5f) Together, these findings indicate that p50 interaction with BARD1 and mono-ubiquitination act to slow S phase progression. Expression of p502KR led to significantly higher numbers of breaks and gaps
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
