Detection of the interaction between Hus1 and Rad9 or Rad1. 1, L40 bearing Hus1 in pHybLex/Zeo vector and Rad9 in pYESTrp2 vector; 2, L40 bearing Hus1 in pHybLex/Zeo vector and Rad1 in pYESTrp2 vector; 3, L40 bearing Rad9 in pYESTrp2 vector and an empty pHybLex/Zeo vector; 4, L40 bearing Hus1 in pHybLex/Zeo vector and an empty pYESTrp2 vector; 5, L40 bearing Rad1 in pYESTrp2 vector and an empty pHybLex/Zeo vector. A, Non-selective medium for detection of interaction; B, The activation of the HIS promoter was tested on plates without Histidine. C, Activation of the LacZ promoter by assay of β-galactosidase activity. Hus1 interacted either with Rad9 (B1, C1) or Rad1 (B2, C2).