SPOP-containing complex regulates SETD2 stability and H3K36me3-coupled alternative splicing

Area of Science:

• Molecular Biology
• Epigenetics
• Cancer Biology

Background:

• Histone H3K36 trimethylation (H3K36me3) is a key epigenetic mark linked to active gene expression, mRNA splicing, and DNA repair.
• SETD2, the primary enzyme responsible for H3K36me3, functions as a tumor suppressor in mammals.
• Dysregulation of epigenetic modifiers like SETD2 is implicated in various cancers.

Purpose of the Study:

• To investigate the regulatory mechanisms controlling SETD2 protein stability.
• To identify proteins interacting with SETD2 and elucidate their role in its regulation.
• To understand the functional consequences of SETD2 regulation by its interacting partners on gene expression and chromatin.

Main Methods:

• Co-immunoprecipitation assays to identify SETD2-interacting proteins.
• Ubiquitination assays (in vivo and in vitro) to assess SETD2 modification.
• Chromatin immunoprecipitation sequencing (ChIP-Seq) to analyze H3K36me3 distribution.
• Western blotting to evaluate protein levels and stability.
• Manipulation of SPOP expression to study its effects.

Main Results:

• SPOP, a component of the CUL3 ubiquitin E3 ligase complex, was identified as a SETD2-interacting protein.
• The SPOP/CUL3 complex mediates polyubiquitination and proteasomal degradation of SETD2, thereby regulating its stability.
• Modulating SPOP levels altered H3K36me3 levels at target genes and influenced H3K36me3-dependent alternative splicing events.
• This study establishes a direct link between SPOP and SETD2 in controlling epigenetic modifications and gene expression.

Conclusions:

• SPOP acts as a negative regulator of SETD2 stability through the ubiquitin-proteasome system.
• The SPOP-SETD2 interaction provides a mechanism for dynamic control of H3K36 trimethylation and its downstream effects on gene expression and splicing.
• These findings highlight a functional interplay between oncogenic SPOP and tumor-suppressive SETD2 in cancer biology.