The transcript cleavage factor paralogue TFS4 is a potent RNA polymerase inhibitor

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• TFIIS-like factors are essential for RNA polymerase (RNAP) processivity and fidelity in archaea and eukaryotes.
• In Sulfolobus solfataricus, TFS1 acts as a cleavage factor, while its paralog TFS4 has evolved inhibitory functions.

Purpose of the Study:

• To investigate the functional diversification of TFIIS-like factors in archaea.
• To elucidate the mechanism of transcription inhibition by TFS4.
• To explore the role of TFS4 in the context of host-virus interactions.

Main Methods:

• Biochemical assays to assess RNAP inhibition by TFS4.
• Site-directed mutagenesis to identify key residues for TFS4 activity.
• Construction and testing of chimeric TFIIS-TFS4 constructs.
• Analysis of TFS4 expression during viral infection.

Main Results:

• TFS4 inhibits transcription initiation and elongation by destabilizing the pre-initiation complex.
• Inhibitory activity is dependent on specific lysine residues in TFS4's zinc ribbon.
• A chimeric TFIIS-TFS4 construct inhibits eukaryotic RNAPII, indicating conserved mechanisms.
• TFS4 expression is upregulated upon Sulfolobus turreted icosahedral virus infection.

Conclusions:

• Archaean TFIIS-like factors exhibit significant functional divergence, with TFS4 evolving potent RNAP inhibition.
• The molecular basis for TFS4-mediated transcription inhibition is conserved across archaea and eukaryotes.
• TFS4 plays a role in the host-virus relationship within Sulfolobus, acting as a defense mechanism against viral infection.