Transcript TRAP = Telomerase Repeat Amplification Protocol

Inactivation of hTERT
transcription by Tax
Julien Daniel, Raphael Doineau, Astrild Vaudaine,
Sebastian Schmidt, Sebastian Olényi
Gabet et al., Oncogene 2003
Leukemia-causing?
- Blood cancer
- telomere dysfunction
generates dicentric and multicentric
chromosomes
- T-cell leukemia virus type
1(HTLV -1)
- 3–5% of infected individuals develop
adult
T-cell leukemia/lymphoma (ATLL)
- oncoprotein Tax
The idea
- telomere dysfunction
observed in solid tumors
- E-boxes also
implicated in the Taxassociated
transcriptional inhibition
of several cellular genes
(p53)
-> Telomeraseinactivation?
TRAP = Telomerase Repeat Amplification
Protocol
Cell lysate
Differential telomere
length or quantity
Detection
(ELISA, X-ray of
radioactively marked
probes, ...)
Amplified, marked telomeres
PCR with
labelling of
telomere
repeats
TRAP = Telomerase Repeat Amplification
Protocol
Cell lysate
Differential telomere
length or quantity
Detection of the original amount
of telomere repeats from the RTPCR-procedure
RT-PCR with
telomereprimers and
detection
Amplification measured by
real-time PCR
➔
Importance of Tax in the decrease of telomerase activity
Effect of Tax on
hTERT promoter-luciferase
➔
➔
Tax reduces
luciferase activity
hTERT is
repressed by Tax
Discussion - Outview
„Paradoxical“ role of TAX:
-
-
activates T-cell proliferation; in normal T-cells, hTERT is
activated
At the same time, it blocks hTERT transcription
Thus, Tax favours chromosome rearrangement and mutation
accumulation, leading to malignant cells
Tax expression is restricted to the pre-malignant stage where
it inhibits the „reparatory effect“ of hTERT
Discussion - Outview
-
Many other forms of cancer are also preceded by a long
latency
There seem to exist other oncogenes exhibiting the same role
as Tax
Thus, better examination of the Tax mechanism may provide
insights into other forms of cancer