Genome-wide function of THO/TREX in active genes prevents R-loop-dependent replication obstacles

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The THO/TREX complex is involved in messenger ribonucleoprotein (mRNP) biogenesis and preventing transcription-associated recombination.
• Its genome-wide distribution and function remain largely uncharacterized.

Purpose of the Study:

• To investigate the genome-wide distribution of the THO/TREX complex and its functional role in yeast.
• To elucidate the role of THO/TREX in transcription elongation and preventing replication obstacles.

Main Methods:

• Chromatin immunoprecipitation (ChIP)-chip assays were performed to determine the genome-wide distribution of Hpr1 (THO component) and Sub2.
• Gene expression analysis was conducted on THO-Sub2 deletion mutants.
• Rrm3 recruitment was assessed in THO mutants, with and without RNaseH1 overexpression.

Main Results:

• THO and Sub2 are distributed genome-wide at active open reading frames (ORFs) in yeast, exhibiting a 5' to 3' gradient.
• THO-Sub2 deletions impact the expression of highly expressed, long, and high G+C-content genes.
• THO mutants show increased Rrm3 recruitment at active genes, which is mitigated by RNaseH1 overexpression, suggesting a role in preventing R-loops.

Conclusions:

• The THO-Sub2 complex has a genome-wide function in transcription elongation and mRNP biogenesis.
• This function is crucial for preventing the accumulation of transcription-mediated replication obstacles, such as R-loops.