Methionine Adenosyltransferase 2B, HuR, and Sirtuin 1 Protein Cross-talk Impacts on the Effect of Resveratrol on Apoptosis and Growth in Liver Cancer Cells

Heping Yang,Yuhua Zheng,Tony W.H Li,Hui Peng,David Fernandez-Ramos,María L Martínez-Chantar,Adriana L Rojas,José M Mato,Shelly C Lu

doi:10.1074/jbc.m113.487157

Abstract

Resveratrol is growth-suppressive and pro-apoptotic in liver cancer cells. Methionine adenosyltransferase 2B (MAT2B) encodes for two dominant variants V1 and V2 that positively regulate growth, and V1 is anti-apoptotic when overexpressed. Interestingly, crystal structure analysis of MAT2B protein (MATβ) protomer revealed two resveratrol binding pockets, which raises the question of the role of MAT2B in resveratrol biological activities. We found that resveratrol induced the expression of MAT2BV1 and V2 in a time- and dose-dependent manner by increasing transcription, mRNA, and protein stabilization. Following resveratrol treatment, HuR expression increased first, followed by SIRT1 and MAT2B. SIRT1 induction contributes to increased MAT2B transcription whereas HuR induction increased MAT2B mRNA stability. MATβ interacts with HuR and SIRT1, and resveratrol treatment enhanced these interactions while reducing the interaction between MATβ and MATα2. Because MATβ lowers the Ki of MATα2 for S-adenosylmethionine (AdoMet), this allowed steady-state AdoMet level to rise. Interaction among MATβ, SIRT1, and HuR increased stability of these proteins. Induction of MAT2B is a compensatory response to resveratrol as knocking down MAT2BV1 potentiated the resveratrol pro-apoptotic and growth-suppressive effects, whereas the opposite occurred with V1 overexpression. The same effect on growth occurred with MAT2BV2. In conclusion, resveratrol induces HuR, SIRT1, and MAT2B expression; the last may represent a compensatory response against apoptosis and growth inhibition. However, MATβ induction also facilitates SIRT1 activation, as the interaction stabilizes SIRT1. This complex interplay among MATβ, HuR, and SIRT1 has not been previously reported and suggests that these proteins may regulate each other's signaling.

Highlights

Methionine adenosyltransferase 2B protein (MAT␤) binds to resveratrol, but it exerts the opposite effects on growth and apoptosis
We reported that both MAT␤ variants (MAT␤V1 and MAT␤V2) are found in the nucleus, and they interact with human antigen R (HuR), a RNA-binding protein that stabilizes its target mRNAs, which include several cyclins [9]
The effects of RSV in liver cancer cells appear to be the exact opposite of MAT␤, which we have shown to be overexpressed in hepatocellular carcinoma (HCC) and to be pro-growth and protect against apoptosis [6]

Summary

Background

Methionine adenosyltransferase 2B protein (MAT␤) binds to resveratrol, but it exerts the opposite effects on growth and apoptosis. Results: Resveratrol induces HuR, SIRT1, and MAT␤ expression MAT␤ is best known for regulation of MATII enzymatic activity, our recent works revealed a much broader role for MAT2B protein in cancer biology. We reported that both MAT␤ variants (MAT␤V1 and MAT␤V2) are found in the nucleus, and they interact with human antigen R (HuR), a RNA-binding protein that stabilizes its target mRNAs, which include several cyclins [9]. Because RSV is growth-suppressive and pro-apoptotic but MAT␤ variants exert the opposite effect in liver cancer cells, we undertook this study to examine how RSV affects MAT2B biology and how MAT2B in turn affects RSV actions. Our results suggest that these proteins may regulate each other’s signaling pathways

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION