trans

POST-TRANSCRIPTIONAL REGULATION IN KINETOPLASTIDS 79
Bloodstream
Procyclic
EP1
EP2
A
B
AAA
AAA
AAA
AAA
AAA
AAA
AAA
AAA
E
X
AAA
AAA
C
AAA
F
G
D
EP protein
Membrane
U-rich 26mer 16mer stem-loop EP1 3-untranslated region EP2 3-untranslated region
FIGURE 4.4
Regulation of EP procyclin expression in Trypanosoma brucei.
half-life in procyclics was about 90 min. Most
half-lives measured have been in the range of
30 min to 2 h. For T. cruzi, half-life estimates are
only available for short and long versions of
the mucin RNAs: the endogenous transcripts
had half-lives of at least 6 h in epimastigotes
and less than 30 min in trypomastigotes. More
information is available about Leishmania
genes: here we have half-lives in log-phase
promastigotes of 84 min for MSPL, about 1 h for
A2, 7 h for TUB and less than 1 h for HSP83 at
26°C. The MSPL transcripts were destabilized
in stationary-phase promastigotes (half-life
17 min) as were TUB transcripts (180 min), and
A2 transcripts are stabilized (half-life 2 h) in
amastigotes. Very short half-lives such as those
seen for EP transcripts in bloodstream-form
T. brucei have not been seen in the other species.
MOLECULAR BIOLOGY