Yeast strains and culture conditions
Yeast cells were grown in YPD (1% yeast extract, 2% peptone, 2%
glucose) at 30°C. Pre-cultures were grown overnight in 250 mL flasks and
shaken at 190 rpm. The next day, pre-cultures were diluted to
OD600 = 0.05 and grown until an OD600 of
~0.5 was reached. Cells were recovered by
centrifugation, flash-frozen in liquid nitrogen and stored at -20 ºC
until needed for Genomic Run-on (GRO) or RNA extraction. Yeast strains
were transformed with centromeric plasmids YCpLac33 and pBBM3 following
a standard protocol (Gietz & Schiestl, 2007). Yeast strains and
plasmids are listed in Supplementary Table S1.
For generation time (GT) estimations, 50 mL of yeast cultures were grown
in 250-mL flasks with shaking (190 rpm) at 30°C. Aliquots were taken
every 30 min in the exponential phase and their OD600(from 0.05 to 0.7) were measured. The GT (in minutes) in the exponential
phase was calculated from growth curves (see Figures 1 and S1).
The median values of cell volumes were calculated by a Coulter-Counter Z
series device (Beckman Coulter, USA). The absolute values in femtolitres
(fL) and relative values are shown in Figures 1 and S1.