SPG-7 is a mitochondrial membrane metalloprotease; knockdown of spg-7 by RNAi results in accumulation of mitochondrially localized GFP and specific upregulation of expression of nuclear-encoded, mitochondrial chaperone proteins HSP-6 and HSP-60 as determined by Phsp-6::GFP and Phsp-60::GFP transgene reporters (both by fluorescence microscopy and western blot) and by northern blot of endogenous hsp-6 mRNA