PRMT1 accelerates cell proliferation, migration, and tumor growth by upregulating ZEB1/H4R3me2as in thyroid carcinoma

Thyroid carcinoma (TC) represents the most prevalent malignancy of the endocrine system. Protein arginine methyltransferase 1 (PRMT1) is a critical member of the protein arginine methyltransferase family in mammals and is involved in multiple biological processes. This study aimed to investigate the function of PRMT1 in TC. In the present study, human TC cell lines (8505C, CAL62, and BCPAP) and a normal human thyroid cell line Nthy‑ori 3‑1 were employed. Small interfering RNA targeting PRMT1 was used to knock down PRMT1 expression in 8505C cells, and PRMT1 overexpression plasmids were transfected into BCPAP cells. Cell viability was assessed using a CCK‑8 and colony formation assays. Apoptosis was measured using flow cytometry and TUNEL assays. Cell migration was assessed using wound healing and Transwell assays. Reverse transcription‑quantitative PCR was used to determine the mRNA expression levels of PRMT1. Western blotting was used to detect the protein expression levels of PRMT1, E‑cadherin, vimentin, H4R3me2as, and zinc‑finger E homeobox‑binding 1 (ZEB1). Notably, PRMT1 expression was elevated in TC (P<0.01). PRMT1 knockdown inhibited TC cell proliferation and migration and concurrently enhanced migration. Furthermore, PRMT1 knockdown suppressed tumor growth and metastasis in a mouse model of TC. PRMT1 downregulation increased E‑cadherin expression and decreased the expression of vimentin, H4R3me2as, and ZEB1 in the TC cells and the mouse model of TC. Conversely, PRMT1 overexpression had the opposite effect on TC malignant characteristics (P<0.05). These findings suggest that PRMT1 knockdown inhibited TC malignancy by downregulating H4R3me2as/ZEB1, thereby highlighting novel therapeutic targets and diagnostic markers for the management of TC.

Different Protein Groups Involved in Transcription Regulation in Development and Housekeeping Genes in Drosophila

Antibodies to histone modifications and an insulator protein involved in the processes of transcription initiation and elongation are mapped in Drosophila polytene chromosomes. The CHRIZ protein (chromatin insulator) and H3K36me3 histone modification (RNA elongation) are detected only in the localization of housekeeping genes (interbands and gray bands of polytene chromosomes) and never in the regions of developmental genes (black bands and large puffs arising from them). Antibodies to H3S10P histone modification, which is associated with the initial elongation of the RNA strand during transcription, are found exclusively in small puffs, but not in housekeeping gene localization sites or large ecdysone-induced puffs, where housekeeping genes are localized. Antibodies to H4R3me2 histone modification (a co-repressor of the ecdysone receptor) are detected only in large ecdysone-induced puffs.

Sirtuin 7-mediated deacetylation of WD repeat domain 77 (WDR77) suppresses cancer cell growth by reducing WDR77/PRMT5 transmethylase complex activity

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.