Fig 2: PARP-1 acts as an active epigenetic memory marker to regulate post-mitotic transcription. Based on our finding we propose the following model of PARP-1 action as an epigenetic mark: PARP-1 remains bound to chromatin during mitosis and facilitates transcription after mitosis by poly(ADP-ribosyl)ating chromatin, effectively opening it. Upon depletion or inhibition of PARP-1, chromatin remains condensed after mitosis, thereby blocking or delaying transcriptional restart. Green triangle indicates NFATC2 transcription factor binding in proximity to PARP-1 binding site.

Fig 3: The distribution of PARP-1 binding sites and NFATC2 consensus between functional groups of genes in human genome. GO enrichment among genes from different categories based on PARP-1 occupancy during mitosis and interphase. Using DAVID software, genes displaying different PARP-1 occupancy patterns during mitosis and interphase were tested separately for enrichment with respect to gene ontology terms including categories for biological processes (bp), molecular functions (mf) and cellular components (cc). The occupancy pattern is indicated on the bottom as follows: the mitotic group (M) has PARP-1 peak(s) in mitosis within 10 kb from TSS, mitotic gene in interphase (M gone in I) had PARP-1 peak(s) in mitosis within 1.5 kb, but lost them during interphase [this region shown to be important for silencing during interphase by PARP-1], mitotic and interphase (M and I) has peaks within 10 kb of TSS in both mitosis and interphase and interphase (I) has peaks in interphase only. An additional GO enrichment test was performed for genes that contained NFATC2 motif within 200 bp of the PARP-1 peak center. Intensity of red shading on the heatmap corresponds to the degree of significance enrichment.