Kinase activity and interactions of Mec1kd variants. (A) HA-tagged Mec1 or Mec1kd proteins (Mec1-HA) were immunoprecipitated with anti-HA antibodies (anti-HA IP) from protein extracts prepared from exponentially growing cells concomitantly expressing Mec1-HA9 and Ddc2-MYC18 (DMP3295/8B), Mec1kd1-HA9 and Ddc2-MYC18 (DMP3296/3C), or Mec1kd2-HA9 and Ddc2-MYC18 (DMP3297/6D) from the MEC1 and DDC2 promoters, respectively, as indicated at the bottom. Kinase assays were performed on anti-HA immunoprecipitates, and the results are shown at the top. The same immunoprecipitates were also analyzed by Western blot assay using the antibodies indicated on the right side of the middle and bottom parts of the panel. (B) Immunoprecipitations with anti-HA (anti-HA IP) or anti-MYC (anti-MYC IP) antibodies were performed on extracts from exponentially growing untreated (−) or MMS-treated (+; 0.02% MMS for 1 h) diploid cells with the genotypes indicated in the top part of the panels. Mec1-HA9 and Mec1-MYC18 were then detected by Western blot analysis of the immunoprecipitates by using anti-HA and anti-MYC antibodies. The genotypes of the strains used were MEC1-HA9/MEC1-MYC18 (DMP2750.1), MEC1/MEC1-MYC18 (YLL447.32), MEC1/MEC1-HA9 (YLL476.34), mec1kd1-HA9/MEC1-MYC18 (DMP2885.4), and mec1kd2-HA9/MEC1-MYC18 (DMP2893.1).