MAF1 represses CDKN1A through a Pol III-dependent mechanism

Area of Science:

• Molecular Biology
• Gene Regulation
• Biochemistry

Background:

• The protein Maf1 (MAF1) is a known repressor of RNA Polymerase III (Pol III)-mediated transcription, primarily by inhibiting the transcription factor IIIB (TFIIIB) complex and Pol III itself.
• The precise mechanisms by which MAF1 influences RNA Polymerase II (Pol II)-mediated transcription, particularly in the context of chromatin structure, remain incompletely understood.

Purpose of the Study:

• To investigate the role of MAF1 in regulating Pol II-mediated transcription and chromatin looping.
• To elucidate the involvement of Pol III recruitment in MAF1-mediated gene activation and chromatin dynamics.

Main Methods:

• Utilized MAF1 knockdown experiments in cellular models.
• Performed chromatin-immunoprecipitation (ChIP) assays to analyze protein binding at gene promoters.
• Assessed gene transcription and chromatin looping through specific molecular assays.

Main Results:

• MAF1 knockdown induced transcription of the CDKN1A gene and associated chromatin looping, accompanied by Pol III recruitment.
• Simultaneous knockdown of MAF1 with Pol III or BRF1 (a TFIIIB subunit) abrogated the observed activation and looping.
• ChIP analysis revealed enhanced binding of Pol III, BRF1, histone-modifying enzymes (CFP1, p300, PCAF), and Pol II components (TBP, POLR2E) to the CDKN1A promoter upon MAF1 knockdown, with these events abolished by Pol III co-knockdown.
• Similar regulatory effects were observed for the GDF15 gene.

Conclusions:

• MAF1 and Pol III play a critical, previously unrecognized role in regulating the activity of protein-coding genes transcribed by Pol II.
• Pol III recruitment is essential for the MAF1-dependent activation of Pol II transcription and associated chromatin looping.
• This study uncovers a novel cross-talk mechanism between Pol III machinery and Pol II transcription regulation.