Biology Reference
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include the chicken (
Sherman et al. 1998
) and the zebra fish (
Fadool et al. 1998
).
It even transformed the flagellate protozoan
Leishmania major
, which indi-
cates that
mariner
has a general ability to “parasitize the eukaryotic genome”
(
Gueiros-Filho and Beverley 1997
), perhaps because host proteins are not
required for successful integration.
At least two different subfamilies of
mariner
were isolated from the human
genome, suggesting multiple horizontal transfers occurred, and
Oosumi et al.
(1995)
suggested that
mariner
could be used as a transformation vector for
humans. A
mariner
vector from fish was genetically engineered to make it more
active in humans; through genetic recombination and site-directed mutagenesis
of a
mariner
-like defective element, a new element called
Sleeping Beauty
was
constructed that had 25-fold higher levels of activity in human cells than the
“standard”
mariner
(
Plasterk et al. 1999
).
Sleeping Beauty
is active in tissue-cul-
ture cells, as well as the germ line of the mouse and zebrafish (
Ivics et al. 2004
).
So far, all
mariner
elements discovered in humans are “molecular fossils
derived from a
mariner
that was long ago active in the genome of a human
ancestor,” with each copy having multiple mutations (
Robertson and Martos
1997
).
Robertson and Zumpano (1997)
found that
mariner
sequences are pres-
ent in all major primate lineages, and estimated that there are
≈
200 copies
of one (
Hsmar1
) in the human genome, as well as
≈
2400 copies of a derived
80-bp inverted repeat structure and
≈
46,000 copies of single inverted repeats,
suggesting that
mariner
had “a considerable mutagenic effect on past primate
genomes.” The human genome is estimated to have been invaded by at least 14
families of TEs and is estimated to have
>
100,000 degenerate copies of TEs (
Smit
and Riggs 1996
). These include elements called
pogo
(originally discovered in
Drosophila
) and
Tigger
, which are related to
Tc1
and
mariner
(
Robertson 1996
).
Despite the successes in transforming chickens, fish and other organisms, rates
of transformation of arthropods with
mariner
vectors have been low (
Lampe
et al. 2000
).
Coates et al. (1995)
found
mariner
could excise in
D. melanogas-
ter
,
D. mauritiana
,
Lucilia cuprina
, and
Bactrocera tryoni
embryos.
Wang et al.
(2000)
showed that
mariner
could mediate excision and transposition in
Bombyx
mori
tissue-culture cells. Later,
mariner
was shown to transform
Aedes aegypti
(
Coates et al. 1998
). Some mutants of the transposase gene from a
mariner
iso-
lated from
Haematobia irritans
were found to have 4- to 50-fold increases in
activity, indicating that
mariner
vectors could be developed that are more active
in arthropods (
Lampe et al. 1999
). Because
mariner
can function in bacteria such
as
Escherichia coli
, it is possible to study basic biochemistry of these elements
and to improve them as genetic tools (
Lampe 2010
).
