RB1 methylation by SMYD2 enhances cell cycle progression through an increase of RB1 phosphorylation.
It is well known that RB functions are regulated by posttranslational modifications such as phosphorylation and acetylation, but the significance of lysine methylation on RB has not been fully elucidated. Our expression analysis of SMYD2 by quantitative real-time polymerase chain reaction showed that expression levels of SMYD2 are significantly elevated in human bladder carcinomas compared with nonneoplastic bladder tissues (P < .0001), and its expression levels in tumor tissues were much higher than those of any other normal tissues. SMYD2 knockdown resulted in the suppression of cancer cell growth, and cell cycle analysis indicated that SMYD2 might play a crucial role in the G(1)/S transition. According to an in vitro methyltransferase assay, we found that SMYD2 methylates RB1 protein, and liquid chromatography-tandem mass spectrometry analysis revealed lysine 810 of RB1 to be methylated by SMYD2. Importantly, this methylation enhanced Ser 807/811 phosphorylation of RB1 both in vitro and in vivo. Furthermore, we demonstrated that methylated RB1 accelerates E2F transcriptional activity and promotes cell cycle progression. SMYD2 is an important oncoprotein in various types of cancer, and SMYD2-dependent RB1 methylation at lysine 810 promotes cell cycle progression of cancer cells. Further study may explore SMYD2-dependent RB1 methylation as a potential therapeutic target in human cancer.
Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Hyun-Soo
HS
Cho
Shinya
S
Hayami
Gouji
G
Toyokawa
Kazuhiro
K
Maejima
Yuka
Y
Yamane
Takehiro
T
Suzuki
Naoshi
N
Dohmae
Masaharu
M
Kogure
Daechun
D
Kang
David E
DE
Neal
Bruce A J
BA
Ponder
Hiroki
H
Yamaue
Yusuke
Y
Nakamura
Ryuji
R
Hamamoto
D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D008745:Methylation; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D001749:Urinary Bladder Neoplasms / Q000235:genetics / Q000378:metabolism*
D016160:Retinoblastoma Protein; D011495:Histone-Lysine N-Methyltransferase; C512569:SMYD2 protein, human