| We found that Tpr 2 binds not only to Rad 9 , but also to Rad 1 and Hus 1 , through its N terminal tetratricopeptide repeat region , as assessed by in vivo and in vitro binding assays . ^^^ However , the in vivo and in vitro interactions of Tpr 2 with Rad 9 were greatly enhanced by the deletion of its C terminal J domain or by a point mutation in the conserved HPD motif in the J domain , though the binding of Tpr 2 to Rad 1 and Hus 1 was not influenced by these J domain mutations . ^^^ |