"To determine whether the transcription of
rnf-121 is regulated by PEK-1 and the UPR pathway in C . elegans , we performed a real-time PCR analysis of the mutant strains
pek-1 (
ok275 ) ,
ire-1 (
v33 ) , and
atf-6 (
ok551 ) , as well as of wild-type worms , treated with the UPR inducers DTT , tunicamycin , and thapsigargin . Although the mRNA levels of
hsp-4 were induced upon tunicamycin or DTT treatment and in
pek-1 (
ok275 ) and
atf-6 (
ok551 ) mutant backgrounds , and abolished in
ire-1 (
v33 ) as shown previously ( Shen et al. , 2001 ) , the levels of
rnf-121 mRNA were largely unaffected ( Figure 3B ) ."