Common genomic elements promote transcriptional and DNA replication roadblocks

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• RNA polymerase II (Pol II) transcription termination is crucial for producing stable noncoding RNAs and controlling pervasive transcription in Saccharomyces cerevisiae.
• The Nrd1p-Nab3p-Sen1p (NNS) pathway is a key mechanism for Pol II transcription termination.

Purpose of the Study:

• To identify factors that determine the efficiency of NNS-mediated transcription termination.
• To understand the interplay between chromatin structure, DNA-binding proteins, and Pol II termination.

Main Methods:

• Genome-wide mapping of 3'-ends of NNS-terminated transcripts.
• Analysis of the impact of nucleosomes and specific DNA-binding proteins on Pol II progression and termination efficiency.
• Investigating the effect of NNS pathway inactivation on Pol II elongation through roadblocks.

Main Results:

• Nucleosomes and DNA-binding proteins (General Regulatory Factors like Reb1p, Rap1p, Abf1p, and Pol III factors) enhance NNS termination by physically blocking Pol II.
• These DNA-bound factors also define Okazaki fragment boundaries during DNA replication.
• Reduced binding of these factors leads to defective NNS termination and Pol II readthrough.
• NNS inactivation allows Pol II to elongate through these roadblocks, highlighting a synergy between NNS and chromatin obstacles.

Conclusions:

• Transcription termination efficiency is influenced by RNA termination signals interacting with chromatin obstacles.
• Common genomic elements serve as boundaries for both DNA replication and RNA synthesis machineries.
• The study reveals a coordinated mechanism involving chromatin, DNA-binding proteins, and the NNS pathway for precise transcription termination.