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Mol Cell Biol, February 1998, p. 944-952, Vol. 18, No. 2
Department of Pharmacology, University of
Nebraska Medical Center, Omaha, Nebraska 68198-6260
Received 9 September 1997/Returned for modification 21 October
1997/Accepted 14 November 1997
Steroid receptor complexes are assembled through an ordered,
multistep pathway involving multiple components of the cytoplasmic chaperone machinery. Two of these components are Hsp70-binding proteins, Hip and Hop, that have some limited homology in their C-terminal regions, outside the sequences mapped for Hsp70 binding. Within this region of Hip is a DPEV sequence that occurs twice; in Hop,
one DPEV sequence plus a partial second sequence occurs. In an effort
to better understand Hip function as it relates to assembly of
progesterone receptor complexes, the DPEV region of Hip was targeted
for mutations. Each DPEV sequence was mutated to an APAV sequence,
singly or in combination. The combined mutation, APAV2, was
further combined with a deletion of Hip's tetratricopeptide repeat
region that is required for Hsp70 binding or with a deletion of Hip's
GGMP repeat. An additional mutant was prepared by truncation of Hip's
DPEV-containing C terminus. By comparing interactions of various Hip
forms with Hsp70, it was determined that mutation of the DPEV sequences
created a dominant inhibitory form of Hip. The mutant Hip-Hsp70 complex
was not prevented from interacting with progesterone receptor, but the
mutant caused a dose-dependent inhibition of receptor assembly with
Hsp90. The behavior of the Hip mutant is consistent with a model in
which Hip and Hop are required to facilitate the transition from an
early receptor complex with Hsp70 into later complexes containing
Hsp90.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutation of Hip's Carboxy-Terminal Region Inhibits
a Transitional Stage of Progesterone Receptor Assembly
*
Corresponding author. Mailing address: Department of
Pharmacology, University of Nebraska Medical Center, Omaha, NE
68198-6260. Phone: (402) 559-8604. Fax: (402) 559-7495. E-mail:
dfsmith{at}mail.unmc.edu.
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