Distinct mammalian SWI/SNF chromatin remodeling complexes with opposing roles in cell-cycle control

Area of Science:

• Cellular biology
• Molecular oncology
• Gene regulation

Background:

• The SWI/SNF chromatin remodeling complex is implicated in tumor suppression.
• Its dual role in gene expression (both positive and negative) complicates understanding its biological functions.
• The complex regulates transcription factor accessibility to proliferation-associated genes.

Purpose of the Study:

• To elucidate how the SWI/SNF complex exerts opposing effects on gene expression and cell-cycle activity.
• To identify the molecular mechanism distinguishing activator and repressor functions of the complex.

Main Methods:

• Investigating the role of ARID protein family variants in SWI/SNF complex assembly.
• Analyzing the association of SWI/SNF variants with activator and repressor complexes.
• Assessing the impact of these assemblies on cell-cycle gene promoter accessibility.

Main Results:

• Two variants of a major ARID protein subunit dictate SWI/SNF complex association with either activators or repressors.
• This subunit choice leads to assemblies with opposing effects on cell-cycle progression.
• The specific complexes modulate the access of transcription factors like E2F1, Tip60, and HDAC1/2/3 to target gene promoters.
• c-Myc was identified as a critical target gene regulated by these complexes.

Conclusions:

• The differential assembly of the SWI/SNF complex, driven by ARID subunit variants, determines its function in gene regulation and cell-cycle control.
• This mechanism provides insight into the complex's tumor suppressor role and its seemingly contradictory roles in gene expression.
• Targeting these specific SWI/SNF assemblies may offer new therapeutic strategies in oncology.