RT Journal Article
SR Electronic
T1 Single-molecule measurements reveal that PARP1 condenses DNA by loop formation
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.09.15.297887
DO 10.1101/2020.09.15.297887
A1 Nicholas A. W. Bell
A1 Philip J. Haynes
A1 Katharina Brunner
A1 Taiana Maia de Oliveira
A1 Maria Flocco
A1 Bart W. Hoogenboom
A1 Justin E. Molloy
YR 2020
UL http://biorxiv.org/content/early/2020/09/15/2020.09.15.297887.abstract
AB Poly(ADP-ribose) polymerase 1 (PARP1) is an abundant nuclear enzyme that plays important roles in DNA repair, chromatin organization and transcription regulation. Although binding and activation of PARP1 by DNA damage sites has been extensively studied, little is known about how PARP1 binds to long stretches of undamaged DNA and how it could shape chromatin architecture. Here, using a combination of single-molecule techniques including magnetic tweezers and atomic force microscopy, we show that PARP1 binds and condenses undamaged, kilobase-length DNA subject to sub-picoNewton mechanical forces. Decondensation by high force proceeds through a series of discrete increases in extension, indicating that PARP1 stabilizes loops of DNA. This model is supported by DNA braiding experiments which show that PARP1 can bind at the intersection of two separate DNA molecules. PARP inhibitors do not affect the level of condensation of undamaged DNA, but act to block condensation reversal for damaged DNA in the presence of NAD+. Our findings establish a mechanism for PARP1 in the organization of chromatin structure.Competing Interest StatementThe PARP inhibitor olaparib is marketed by AstraZeneca. K.B., T.M.O. and M.F. are employees of AstraZeneca. T.M.O. and M.F. are shareholders of AstraZeneca. N.A.W.B. was funded by an AstraZeneca-Crick collaborative grant (FC001632). The other authors declare no conflict of interest.