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Transcription-mediated hyper-recombination in HOT1
Naomi Serizawa1, Takashi Horiuchi, Takehiko Kobayashi
1National Institute for Basic Biology, School of Life Science, 38 Nishigonaka, Myodaijicho, Okazaki, 444-8585, Japan.
Summary
Increased RNA polymerase I (PolI) transcription in the HOT1 hotspot significantly boosts mitotic recombination in yeast. This suggests transcription levels directly control recombination efficiency, with Fob1p acting as a transcriptional activator.
Area of Science:
- Molecular Biology
- Genetics
- Yeast research
Background:
- Recombination hotspots, like yeast's HOT1, enhance DNA recombination.
- HOT1 contains a RNA polymerase I (PolI) promoter crucial for ribosomal RNA gene (rDNA) transcription.
- PolI transcription is implicated in HOT1's recombination stimulation, but the exact mechanism is unclear.
Purpose of the Study:
- To investigate the direct role of PolI transcription in stimulating recombination at the HOT1 hotspot.
- To determine if transcription levels, rather than other cellular effects, drive recombination enhancement.
Main Methods:
- Created a yeast strain (rdnDeltaDelta) with deleted rDNA repeats to highly activate PolI transcription at HOT1.
- Quantified HOT1 transcription levels and associated recombination activity in the engineered strain compared to wild-type.
- Assessed the requirement of Fob1 protein in the highly transcribed rdnDeltaDelta strain.
Main Results:
- HOT1 transcription increased ~14-fold in the rdnDeltaDelta strain compared to wild-type.
- Recombination activity stimulated by HOT1 also increased ~15-fold in the rdnDeltaDelta strain.
- Fob1p, essential for HOT1 transcription and recombination in wild-type, was not required in the rdnDeltaDelta strain.
Conclusions:
- The efficiency of recombination at the HOT1 hotspot is directly determined by the level of PolI transcription.
- Fob1p likely functions as a PolI transcriptional activator for HOT1 in wild-type yeast strains.