FIGURE 3: Mec1 mediates the carbon source dependent induction of Rnr3 independently of its DNA damage response network. (A) Key components of the Mec1 checkpoint response network involved in RNR regulation [19]. Blue arrows and red bars denote a positive and inhibitory impact on the indicated gene or protein. (B) Strains of the indicated genotypes (Table S1) were cultured in YPD, YPG, and YPD supplemented with HU (10 mM) or MMS (0.01%). WCE samples were prepared from cells in log phase (YPD and YPG) or following 2 hours exposure to HU or MMS and subjected to Western blot analysis using α-GFP antibodies. Tubulin was used as a loading control. Red box: Mutations that abolish the DDR dependent Rnr3 induction. (C) RAD53-GFP cells were cultured in YPD, YPG, and YPD supplemented with HU (10 mM) or MMS (0.01%). WCE samples were prepared from cells in log phase (YPD and YPG) or following 2 hours exposure to HU or MMS and subjected to Western blot analysis using α-GFP antibodies. (D) WCE samples prepared from the indicated strains (Table S1) grown to mid-log phase in YPG were subjected to Western blot analysis using α-GFP antibodies. Tubulin was used as a loading control.

19. Tsaponina O, Barsoum E, Åström SU, and Chabes A (2011). Ixr1 is required for the expression of the ribonucleotide reductase Rnr1 and maintenance of dNTP pools. PLoS Genet 7(5). doi: 10.1371/journal.pgen.1002061