Volume 422, Issue 1, 1 January 2023, 113413Author links open overlay panelAbstractBackground

Protein arginine methyltransferase 6 (PRMT6) is a type I arginine methyltransferase that asymmetrically dimethylates histone H3 arginine 2 (H3R2me2a). However, the biological roles and underlying molecular mechanisms of PRMT6 in colorectal cancer (CRC) remain unclear.

Methods

PRMT6 expression in CRC tissue was examined using immunohistochemistry. The effect of PRMT6 on CRC cells was investigated in vitro and in vivo. Mass spectrometry, co-immunoprecipitation and GST pulldown assays were performed to identify interaction partners of PRMT6. RNA-seq, chromatin immunoprecipitation, Western blot and qRT-PCR assays were used to investigate the mechanism of PRMT6 in gene regulation.

Results

PRMT6 is significantly upregulated in CRC tissues and facilitates cell proliferation of CRC cells in vitro and in vivo. Through RNA-seq analysis, CDKN2B (p15INK4b) and CCNG1 were identified as new transcriptional targets of PRMT6. PRMT6-dependent H3R2me2a mark was predominantly deposited at the promoters of CDKN2B and CCNG1 in CRC cells. Furthermore, PRMT5 was firstly characterized as an interaction partner of PRMT6. Notably, H3R2me2a coincides with PRMT5-mediated H4R3me2s and H3R8me2s marks at the promoters of CDKN2B and CCNG1 genes, thus leading to transcriptional repression of these genes.

Conclusions

PRMT6 functionally associates with PRMT5 to promote CRC progression through epigenetically repressing the expression of CDKN2B and CCNG1. These insights raise the possibility that combinational intervention of PRMT6 and PRMT5 may be a promising strategy for CRC therapy.

Section snippetsCredit author statement

Yuzhong Chen: Methodology, Software, Data curation, Investigation. Wanqing Liang: Data curation, Software. Jun Du: Investigation, Validation. Jiachi Ma: Visualization. Rongrui Liang: Software, Resources. Min Tao: Conceptualization, Resources, Writing - original draft, Writing - review & editing.

Cell lines and cell culture

HCT116 and SW620 cell lines were obtained from the Cell Bank of Type Culture Collection of Chinese Academy of Sciences (Shanghai, China). HCT116 and SW620 cells were cultured in McCoy's 5 A medium (Life Technologies) and Roswell Park Memorial Institute (RPMI) 1640 medium (HyClone), respectively. HEK 293 T cells were cultured in Dulbecco's modified Eagle's medium (DMEM; Gibco). All these cell lines were incubated at 37 °C in a humidified atmosphere containing 5% CO2 and supplemented with 10%

Expression of PRMT6 in CRC and its clinical significance

To define the role of PRMT6 in CRC, we first asked whether PRMT6 is aberrantly expressed in CRC tissues. The expression of PRMT6 and its substrate H3R2me2a in CRC tissue was detected by IHC staining of tissue microarrays (No. HColA160CS01) cores from 80 cases of CRC patients, including 80 tumor and 80 adjacent normal tissues. Immunoreactive signal of PRMT6 was observed in tumor cells, and located in both the nucleus and cytoplasm of tumor cells, whereas H3R2me2a was preferentially expressed in

Discussion

PRMT6 is a type I PRMT that asymmetrically dimethylates protein substrates on arginine residues and exerts important roles in epigenetic modulation of gene expression [34]. In the present study, we observed that PRMT6 is upregulated in CRC tissues, and correlated with higher histological tumor grade, tumor size, lymph node metastasis and tumor stage. Although recent studies reported increased PRMT6 expression in several types of cancers, few studies have focused on the modulation of PRMT6 [15].

Conclusions

These findings, thereby, reveal that PRMT5 and PRMT6 reciprocally interact with one each other and collaborate as a functional unit to drive the progression of CRC through epigenetically silencing the expression of CDKN2B (p15INK4b) and CCNG1. We also show that combined treatment with PRMT5i and PRMT6i exhibited a synergistic anti-proliferative effect on CRC cells in vitro compared to either treatment alone. Collectively, our findings not only reveal new insights into the pathological

Funding

This study was financially supported by the Science and Technology Plan Project of Suzhou (SLT201913), the Beijing Xisike Clinical Oncology Research Fundation (YXD2019-227), the Horizontal Research Fundation of Soochow University (P142900221), the Natural Science Foundation of Anhui Province (2108085QH344), and Natural Science Foundation of Bengbu Medical College (2020byzd081).

Availability of data and materials

The datasets used in the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

Written informed consent was obtained from all patients and the study was approved by the Ethics Committee of Bengbu Medical College.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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