Worm Breeder's Gazette 10(2): 137

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

An hsp70 Gene Subfamily Encoding Two grp78-like Proteins

Mark F.P. Heschl and David L. Baillie

We have been characterizing some of the genes from the hsp70 
multigene family.  We have recently sequenced two additional members 
of this family.  The hsp70C gene is non-heat inducible and 
constitutively expressed, its mRNA is most abundant at the L1 larval 
stage.  The hsp70C protein shares a high degree of identity with the 
rat grp78 protein (77% at the amino acid level).  The rat grp78 
protein is related to the hsp70 family and is found within the 
endoplasmic reticulum (Munro and Pelham, 1986, Cell 46, 291).  The 
expression of the grp78 gene is enhanced when the cell or organism is 
starved of glucose.  The hsp70C protein has a long, hydrophobic leader 
sequence and the COOH-terminal ER-retention signal sequence KDEL 
characteristic of the rat grp78 protein.  Therefore, we conclude that 
the hsp70C gene is the grp78 equivalent in C.  elegans.In a comparison 
with the hsp70C gene from C.  briggsae, a high degree of homology in 
the coding and noncoding regions is observed.  The 5' regulatory 
region of the two genes share several conserved blocks of sequences 
encompassing a heat shock element and copies of mammalian virus core 
enhancer sequences.  One of these regions is highly conserved (
approximately 80%) with a sequence in the rat grp78 regulatory region. 
This region in the rat grp78 regulatory region is protected during 
nuclease footprinting studies (A. S.  Lee, personal communication).  
We propose that this region may be involved in the glucose-mediated 
Another member of the hsp70 family characterized is the highly heat 
inducible gene hsp70D.  We find that the hsp70D gene is closely 
related to both the hsp70C and grp78 genes (76% and 71% at the amino 
acid level respectively).  As such, we identify the hsp70D gene as the 
first highly heat inducible variety of the grp78 subfamily.  The COOH-
terminal sequence is HDEL and not KDEL found in the hsp70C protein.  
Histidine is a conservative substitution of lysine and may function as 
an ER-retention signal.  Only the last half of the hsp70D gene has 
been sequenced so we are unable to determine if the hsp70D gene, like 
the hsp70C gene, has a long, hydrophobic leader sequence.