The conformational flexibility of the H4 C-terminal tail is essential for growth. (A) Illustration of the glucose shut-off strategy. Expression of plasmid borne wild-type (WT) H3/H4 under the control of the pGAL1/10 promoters in the W1588 genetic background is shut off by the addition of glucose leaving only the integrated copies of WT, G94A and G94P H4 expressed. (B) Integrated H4G94P forms colonies with low efficiency upon repressing expression of WT histones. Identical numbers of cells from strains MCY091 (H4), MCY094 (H4G94A), and MYC097 (H4G94P) were grown in galactose and serially diluted (5 × dilutions) onto plates containing glucose or galactose. (C) As in (B), but strains were grown in glucose for 5.5 h prior to plating. All media lacked uracil (−Ura) to maintain selection for the URA3 marked plasmid expressing WT H3/H4. Plates were photographed after 3 days.