Tob2 phosphorylation regulates global mRNA turnover to reshape transcriptome and impact cell proliferation

Area of Science:

• Molecular Biology
• RNA Biology
• Cell Biology

Background:

• Tob2 protein regulates mRNA deadenylation by interacting with Caf1 deadenylase and poly(A)-binding protein (PABP).
• Tob2 phosphorylation influences its PABP-binding ability and deadenylation function, but the responsible kinase and downstream effects were unknown.

Purpose of the Study:

• To identify the kinase(s) that phosphorylate Tob2.
• To investigate the impact of Tob2 phosphorylation on the transcriptome and its anti-proliferative function.

Main Methods:

• Mass spectrometry
• Poly(A) size-distribution profiling
• Transcriptome-wide mRNA turnover analyses
• Cell proliferation assays

Main Results:

• c-Jun amino-terminal kinase (JNK) phosphorylates Tob2 at multiple sites, weakening Tob2-PABP interaction.
• JNK-independent phosphorylation at serine 254 (S254) enhances Tob2-PABP interaction and deadenylation activity.
• The S254D phosphomimetic mutation accelerates mRNA deadenylation and decay globally, particularly for cell cycle-related transcripts.
• Tob2-S254D enhances anti-proliferation, revealing a phosphorylation-dependent mechanism for Ccr4-Not complex recruitment.

Conclusions:

• Tob2 phosphorylation, particularly at S254, is a critical regulator of mRNA deadenylation and decay.
• Phosphorylation-dependent recruitment of the Ccr4-Not complex by Tob2 reprograms the transcriptome and suppresses cell proliferation.