The Ubiquitin-like with PHD and Ring Finger Domains 1 (UHRF1)/DNA Methyltransferase 1 (DNMT1) Axis Is a Primary Regulator of Cell Senescence

Abstract

Edited by John M. DenuAs senescence develops, cells sequentially acquire diverse senescent phenotypes along with simultaneous multistage gene reprogramming. It remains unclear what acts as the key regulator of the collective changes in gene expression at initiation of senescent reprogramming. Here we analyzed time series gene expression profiles obtained in two different senescence models in human diploid fibroblasts: replicative senescence and H 2 O 2 -induced senescence. Our results demonstrate that suppression of DNA methyltransferase 1 (DNMT1)-mediated DNA methylation activity was an initial event prior to the display of senescent phenotypes. We identified seven DNMT1-interacting proteins, ubiquitin-like with PHD and ring finger domains 1 (UHRF1), EZH2, CHEK1, SUV39H1, CBX5, PARP1, and HELLS (also known as LSH (lymphoid-specific helicase) 1), as being commonly down-regulated at the same time point as DNMT1 in both senescence models. Knockdown experiments revealed that, among the DNMT1-interacting proteins, only UHRF1 knockdown suppressed DNMT1 transcription. However, UHRF1 overexpression alone did not induce DNMT1 expression, indicating that UHRF1 was essential but not sufficient for DNMT1 transcription. Although UHRF1 knockdown effectively induced senescence, this was significantly attenuated by DNMT1 overexpression, clearly implicating the UHRF1/DNMT1 axis in senescence. Bioinformatics analysis further identified WNT5A as a downstream effector of UHRF1/DNMT1-mediated senescence. Senescence-associated hypomethylation was found at base pairs ؊1569 to ؊1363 from the transcription start site of the WNT5A gene in senescent human diploid fibroblasts. As expected, WNT5A overexpression induced senescent phenotypes. Overall, our results indicate that decreased UHRF1 expression is a key initial event in the suppression of DNMT1-mediated DNA methylation and in the consequent induction of senescence via increasing WNT5A expression.

Overexpression of UHRF1 promotes silencing of tumor suppressor genes and predicts outcome in hepatoblastoma

“…In order to assess the effect of UHRF1 depletion on the transcriptome, we performed RNA sequencing of HB cells upon UHRF1 knockdown. As expected, we found UHRF1 to be strongly downregulated and known UHRF1-repressed target genes [ 27 – 29 ] to be upregulated after UHRF1 knockdown, thus emphasizing the significance of our RNA sequencing results (Fig. 4 a).…”

Negative Regulation of p53-Induced Senescence by N-WASP Is Crucial for DMBA/TPA-Induced Skin Tumor Formation

“…Particularly in untreated skin, this increase was striking, because normal epidermis displayed no detectable p16Ink4a expression, as observed also by others (21). Also the reduction of DNMT1 protein can be considered as a senescence marker as DNMT1 protein is decreased in senescent fibroblasts (11,22,23) and mouse keratinocytes (as previously discussed). Moreover, the inhibition of DNMT1 promotes senescence in these cells (11, 22, 23, s.a.).…”

“…The DNA maintenance methylation methyltransferase, DNMT1, is a primary regulator of cell senescence and p16Ink4a (9)(10)(11). Several evidences pointed to DNMT1 as an additional effector of N-WASP in senescence regulation.…”

UHRF1 is required for basal stem cell proliferation in response to airway injury

“…A recent study reports that UHRF1 can suppress IMR90 fibroblast senescence, and senescence induced by UHRF1 knockdown is partially dependent on reduced expression of DNMT1 [28]. To examine global DNA methylation changes induced by UHRF1, we performed DNA dot blot assays using a 5-methylcytosine antibody.…”