Transcription profiling by array of Yeast strain BY4741 treated with alpha -factor mating pheromone to investigate nucleosome plasticity during cell cycle

Yeast strain BY4741 was grown overnight at 30C in YPD rich media. The yeast culture was diluted to an OD600 of 0.1 using fresh YPD media and further grown until an OD600 of 0.2. Then, alpha -factor mating pheromone (GenScript) was added to a final concentration of 10 uM to allow cell synchronization at G1 phase. After 2.5 h, the alpha-factor was removed by harvesting the cells for 10 min at 6000 rpm and decanting supernatant. The arrested cells were inoculated in fresh YPD rich medium to be released from G1-arrest. Samples were collected at 0, 30, 40, 50, and 70 mins, 7.5 ml samples were collected for RNA extraction while 40 ml samples were taken for nucleosomal DNA preparation and for flow cytometry (FACS). Samples for RNA isolation were collected by pipetting the culture directly into 15-ml Falcon tubes containing 7.5 ml of icy-water to quickly chill the cells. Cells were harvested by spinning for 3-4 min at 6000 rpm, frozen in liquid N2 and stored at - 80C. Total cellular RNA was extracted using the RNeasy kit (Qiagen), following the manufacturer’s instructions with the spheroplasting protocol. Purified RNA samples were quantified by Qubit fluorometer (Invitrogen, Inc.) and Nanodrop spectrophotometer (Thermo Scientific, Inc.). The total RNA was hybridized to Affymetrix GeneChip Yeast Genome 2.0 arrays for gene expression analysis.

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