Abstract
The histone transmethylase complex comprising WD repeat domain 77 (WDR77) and protein arginine methyltransferase 5 (PRMT5) catalyzes dimethylation of H4R3 (H4R3me2) and drives cancer cell proliferation and migration, but its regulation is not fully understood. Here, we report that sirtuin 7 (SIRT7) directly deacetylates WDR77 and that this deacetylation interferes with the WDR77-PRMT5 interaction and suppresses proliferation of human colon cancer HCT116 cells. Using co-expression in HEK293T cells and co-immunoprecipitation assays, we observed that SIRT7 deacetylates WDR77 at Lys-3 and Lys-243, which reduced of WDR77's interaction with PRMT5. More importantly, this reduction suppressed the transmethylase activity of the WDR77/PRMT5 complex, resulting in a reduction of the H4R3me2 modification. Rescue of the WDR77-KO HCT116 cells with a WDR77-2KR (K3R and K243R) variant yielded cell migration and proliferation rates that were significantly lower than those of WDR77-KO HCT116 cells rescued with WT WDR77. In summary, SIRT7 is a major deacetylase for WDR77, and SIRT7-mediated deacetylation of WDR77 at Lys-3 and Lys-243 weakens the WDR77-PRMT5 interaction and activity and thereby suppresses growth of cancer cells.
Highlights
The histone transmethylase complex comprising WD repeat domain 77 (WDR77) and protein arginine methyltransferase 5 (PRMT5) catalyzes dimethylation of H4R3 (H4R3me2) and drives cancer cell proliferation and migration, but its regulation is not fully understood
We report that sirtuin 7 (SIRT7) directly deacetylates WDR77 and that this deacetylation interferes with the WDR77–PRMT5 interaction and suppresses proliferation of human colon cancer HCT116 cells
WDR77 is a WD-repeat protein that can interact with protein arginine methyltransferase 5 (PRMT5)2 and form a higherorder tetrameric complex while acting independently as an androgen receptor cofactor (p44) that is overexpressed in prostate cancer cells [17]
Summary
Few SIRT7 targets have been reported in literature. We searched for more potential targets of SIRT7 through purification and MS and found that WDR77 may be a new target of SIRT7 (Fig. 1A). Endogenous PRMT5 interacted less strongly with FLAG-WDR77 when we overexpressed HAtagged SIRT7 in HEK293T cells (Fig. 4B), consistent with the results of the WDR77 deacetylation by SIRT7. The results of RTqPCR showed that these genes were down-regulated in SIRT7 KD cells consistent with the up-regulated levels of H4R3me in SIRT7 KO cells (Fig. 6A), and the mRNA expression levels of these genes were decreased in WDR77-WT cells but remained at higher levels in WDR77–2KR cells (Fig. 6C). We performed a wound-healing assay and still observed a significantly reduced rate of closure in the WDR77–2KR cells compared with that in the WDR77-WT cells (Fig. 6E). We observed much less colony formation in WDR77–2KR cells compared with WDR77-WT cells when performing colony formation assays (Fig. 6F) Taken together, these results demonstrated that WDR77 deacetylation influences cancer cell proliferation by altering WDR77/PRMT5 complex activity
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