Figure 4.

SKY1 is not essential for vegetative growth but is required for phosphorylation of metazoan SR proteins expressed in yeast. (A) Effect of SKY1 deletion (sky1Δ) on cell growth. SKY1 was precisely deleted from two yeast strains, YCS2A (a) or YCS19 (b). As shown in the diagram on the left, the wild-type parent and sky1Δ strains were transformed with either the pSKY1 plasmid expressing a genomic copy of the SKY1 gene in the pRS316 vector or the pRS316 vector alone. Note that the slow growth (small colony size in b) caused by the SKY1 deletion in the YCS19 strain was specifically complemented by pSKY1. (B) SRp55/B52 was expressed in a wild-type or sky1Δ strain and was analyzed as in Fig. 1B.