Fig. 5.

How many Ser5 coding letters suffice for fission yeast growth? (A) Chimeric S5-S5A CTDs. Serial fivefold dilutions of liquid cultures of S. pombe strains with the indicated chromosomal rpb1-CTD alleles were spotted on YES agar medium. The plates were incubated at the indicated temperatures and photographed after 6 d (20 °C), 4 d (25 °C), 2 d (34 °C), or 2.5 d (30 °C and 37 °C). (B) Influence of Ser5 content on CTD phosphorylation. Extracts of CTD-S5/S5A strains expressing Rpb1 with chimeric CTD composed of a block of Ser5- and S5A-containing heptads fused to Rpb1 residue 1577 were resolved by SDS/PAGE. The polypeptides were transferred to membranes and probed by Western blotting with phospho-specific polyclonal Ser2-P and Ser5-P antibodies or monoclonal Ser7-P antibody (4E12) as specified. Immunoblotting with 8WG16 and Spt5 antibodies served as loading controls. The number of consensus Ser5-containing heptads in each strain is indicated above the lanes.