Role of Rad23 and Dsk2 in Nucleotide Excision Repair and Spindle Pole Body Duplication

摘要

The three yeast UBL-UBA proteins, Rad23, Ddi1 and Dsk2 bind both ubiquitin and the proteasome. They are not essential for viability and some redundancy in terms of stabilization of ubiquitinated substrates has been shown, suggesting that they may have overlapping functions. Here we showed that Rad23 is indeed redundant with both Ddi1 and Dsk2 for cell cycle related roles. Surprisingly, Ddi1 and Dsk2 do not show any redundancy but the triple deletion shows a synthetic defect, suggesting that Rad23 has at least two different roles in cell cycle progression during G2/M. In addition, we found that these putative roles do not include a role in SPB duplication or spindle dynamics. In addition, we show that a tetra-ubiquitin chain is able to bind several UBL-UBA proteins at once, which might explain the redundancies observed, as well as suggesting that these multiple interactions might be relevant for efficient but regulated delivery of ubiquitinated substrates to the proteasome.