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Insights in Enzyme Research
ISSN: 2573-4466
E u r o S c i C o n C o n g r e s s o n
Enzymology and
Molecular Biology
A u g u s t 1 3 - 1 4 , 2 0 1 8
P a r i s , F r a n c e
Enzymology 2018
G
enome stability in human cells requires proper maintenance of telomere length at both ends of individual linear chromosomes.
During cell division, telomerase activity adds telomeric repeats to telomeres. Past studies have revealed profound insights
into the cellular functions of the telomerase holoenzyme. However, due to very low abundance of functional telomerase and
limited accuracy in quantifying its activity, fundamental thermodynamic and kinetic properties of human telomerase remain
uncharacterized. By using newly developed technologies to analyse both endogenous and recombinant telomerase holoenzymes,
we demonstrate that each holoenzyme complex contains two different types of active sites. Surprisingly, both types of active
sites turn inactive after each round of processive extension reaction, named single-run catalysis. The first type of active sites
turns off ~40-fold quicker than the other and exhibits higher affinity to a typical substrate. When the first site is in action, the
second site remains unoccupied. The two sites thus act in tandem with the faster site performing before the slower one. The
inactive enzyme is reactivated by intracellular telomerase-activating factors (iTAFs) available in multiple different types of cells
we have tested. Together, the single-run catalysis and the iTAFs serve as an intrinsic brake to ensure that each fully active dimeric
holoenzyme is digitally controlled in the number of telomeres it can work on. Such exquisite kinetic control of telomerase activity
is expected to play important roles in normal cell physiology and cancer biology
.
qxjiang@ufl.eduNovel ON-OFF kinetics for human telomerase
holoenzyme
Qiu-Xing Jiang
1
, Mohammed D Sayed
2, 3
, Ao Cheng
2, 4
,
Gaya Yadav
2,1
, Andrew T Ludlow
2, 3
, Jerry W Shay
2
and
Woodring E Wright
2
1
University of Florida, Florida, USA
2
University of Texas Southwestern Medical Center, Texas, USA
3
University of Michigan, Ann Arbor, Michigan, USA
4
University of Minnesota, Minnesota, USA
Insights Enzyme Res 2018, Volume 2
DOI: 10.21767/2573-4466-C1-003