L. Quijada et al., ANALYSIS OF POSTTRANSCRIPTIONAL REGULATION OPERATING ON TRANSCRIPTIONPRODUCTS OF THE TANDEMLY LINKED LEISHMANIA-INFANTUM HSP70 GENES, The Journal of biological chemistry, 272(7), 1997, pp. 4493-4499
The genomic organization and expression of the hsp70 genes of Leishman
ia infantum were examined. In the cluster there are at least six copie
s of the hsp70 genes arranged in a head-to-tail tandem of 3.8-kilobase
repetition units. The hsp70 gene copy (gene 6) located at the 3' end
of the tandem has a 3'-untranslated region highly divergent in sequenc
e relative to the 3'-untranslated region of the rest of hsp70 gene cop
ies (genes 1-5). Nuclease S1 protection assays indicated that the stea
dy-state level of the mRNAs derived from gene 6 is about SO-fold more
abundant than the transcript level derived from genes 1-5. Nuclear run
-on assays showed, however, that all hsp70 genes are transcribed at si
milar rates. Thus, it is likely that the differences in the steady-sta
te levels of the transcripts from the hsp70 genes should be associated
with variations in their processing or maturation rates. While the ab
undance of the mRNAs derived from hsp70 genes 1-5 is increased by heat
shock, the hsp70 gene 6 mRNA level remains unaffected. Our data showe
d that ongoing protein synthesis is required for the maintenance of th
e heat inducement, depicting, thus, a post-transcriptional mechanism o
f positive regulation involving a labile protein factor that would be
either induced or activated during heat shock.