SCAF4 and SCAF8, mRNA Anti-Terminator Proteins

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• RNA Processing

Background:

• Accurate messenger RNA (mRNA) termination is crucial for proper gene expression.
• Alternative polyadenylation (polyA) sites can lead to premature termination and non-functional transcripts.

Purpose of the Study:

• To investigate the roles of SCAF4 and SCAF8 proteins in mRNA termination and polyadenylation site selection.
• To elucidate the mechanism by which SCAF4 and SCAF8 regulate transcription termination.

Main Methods:

• Analysis of SCAF4 and SCAF8 protein binding to the phosphorylated RNAPII C-terminal repeat domain (CTD).
• Investigation of polyA site selection and mRNA termination in human cells with concomitant SCAF4 and SCAF8 knockout.
• Characterization of independent functions of SCAF4 and SCAF8 in transcription elongation and termination.

Main Results:

• SCAF4 and SCAF8 act as anti-terminators, suppressing the use of early, alternative polyA sites.
• These proteins bind to hyper-phosphorylated RNAPII CTD (Ser2 and Ser5) at alternative polyA sites.
• Concomitant knockout of SCAF4 and SCAF8 causes altered polyA selection, early termination, truncated mRNAs, and is cell lethal.
• SCAF8 functions as an RNAPII elongation factor, while SCAF4 is essential for canonical termination when SCAF8 is present.

Conclusions:

• SCAF4 and SCAF8 redundantly suppress early mRNA termination but have distinct non-essential functions.
• Together, SCAF4 and SCAF8 orchestrate the transition between RNAPII elongation and termination.
• These proteins ensure correct polyA site selection and transcriptional termination in human cells, maintaining gene expression fidelity.