BBMB Research Seminars

March 1, 2007
Elizabeth Craig
Department of Biochemistry
University of Wisconsin-Madison
"Versatile Chaperone Mmachineries: Networks of Hsp70s and J-proteins"
1414 Molecular Biology Buidling
4:10 p.m.

Highly conserved molecular chaperones function in a wide variety of cellular processes, including protein folding, translocation of proteins across membranes and remodeling of protein complexes. J-proteins are obligate partners of Hsp70s that act via their J-domains to stimulate Hsp70's ATPase activity, stabilizing their interactions with client proteins. In addition many J-proteins contain additional domains, some of which are capable of binding client proteins and allowing J-proteins to "deliver" them to their partner Hsp70. Like Hsp70s, J-proteins are encoded by large multigene families. Our results indicate that certain Hsp70s and J-proteins have evolved to function in specialized cellular processes. For example, Jjj1, plays an important role in biogenesis of 60S ribosomal subunits, likely facilitating the dissociation of factors from preribosomes to generate subunits competent for translation. In contrast, others are multifunctional. For example, the most abundant J-protein of the yeast cytosol, Ydj1, functions in multiple cellular processes. Surprisingly, however, expression of only a J-domain at normal levels is capable of rescuing the severe growth defect caused by the absence of Ydj1. Thus many functions carried out by this highly conserved and complex J-protein require only the capacity to stimulate Hsp70s ATPase activity, not the "delivery" of client proteins.