The hsp70-interacting protein Hip participates in the assembly pathway
for progesterone receptor complexes, Duping assembly Nip appears at e
arly assembly stages in a transient manner that parallels hsp70 intera
ctions, In this study, a cDNA for human Hip was used to develop variou
s mutant Hip forms in the initial mapping of functions to particular H
ip structural elements, Hip regions targeted for deletion and/or trunc
ation included the C-terminal region (which has some limited homology
with Saccharomyces cerevisiae Stil and its vertebrate homolog p60), a
glycine-glycine-methionine-proline (GGMP) tandem repeat, and a tetratr
icopeptide repeat (TPR), Binding of Hip to hsp70's ATPase domain was L
ost with deletions from the TPR and from an adjoining highly charged r
egion; correspondingly, these Hip mutant forms were not recovered in r
eceptor complexes, Truncation of Hip's Still-related C terminus result
ed in Hip binding to hsp70 in a manner suggestive of a misfolded pepti
de substrate; this hsp70 binding was localized to the GGMP tandem repe
at, Mutants lacking either the C terminus or the GGMP tandem repeat we
re still recovered in receptor complexes, Truncations from Hip's N ter
minus resulted in an apparent loss of Hip homo-oligomerization, but th
ese mutants retained association with hsp70 and were recovered in rece
ptor complexes. This mutational analysis indicates that Rip's TPR is r
equired For binding of Rip with hsp70's ATPase domain, In addition, so
me data suggest that hsp70's peptide-binding domain may alternately or
concomitantly bind to Hip's GGMP repeat in a manner regulated by Stil
-related sequences.