Protein arginine methyltransferase 5 is a key regulator of the MYCN oncoprotein in neuroblastoma cells.
Bottom Line: Immunoblotting of NB cell-lines shows that high PRMT5 expression is strongly associated with MYCN-amplification (P < 0.004, Mann-Whitney U-test) and immunohistochemical analysis of primary NBs reveals that whilst PRMT5 protein is ubiquitously expressed in the cytoplasm of most cells, MYCN-amplified tumours exhibit pronounced nuclear PRMT5 staining.PRMT5 knockdown in MYCN-overexpressing cells, including the SHEP-21N cell-line with inducible MYCN expression leads to a dramatic decrease in MYCN protein and MYCN-associated cell-death in SHEP-21N cells.Together our studies implicate PRMT5 in a novel mode of MYCN post-translational regulation and suggest PRMT5 plays a major role in NB tumorigenesis.
Affiliation: Cancer Epigenetics Laboratory University of Bristol, Bristol BS8 1TD, UK.Show MeSH
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Mentions: Both SK-N-BE(2)C and NGP cells are known to have MYCN amplification and high MYCN protein expression, whereas SH-SY5Y cells do not, suggesting a relation between PRMT5 and MYCN expression. Examination of PRMT5 expression in NB cell-lines confirmed that MYCN over-expression was associated with higher PRMT5 protein levels (P = 0.004, Mann–Whitney U test) (Figure 3A–B). At the RNA level, in silico analysis shows that high PRMT5 transcripts also correlate with MYCN amplification status (P = 2.0e−08) and with poor overall prognosis (P = 2.2e−08) (Figure S2A). Notably, however, elevated PRMT5 mRNA levels were also associated with poor outcome in MYCN-unamplified tumours (P = 1.7e−06) (Figure S2B), alluding to a possible MYCN-independent oncogenic role for PRMT5 in NB. For example, PRMT5 has been shown to regulate cell-cycle progression (Scoumanne et al., 2009) and modify other proteins involved in NB tumorigenesis, such as E2F-1 and p53 (Jansson et al., 2008; Cho et al., 2012).
Affiliation: Cancer Epigenetics Laboratory University of Bristol, Bristol BS8 1TD, UK.