The Mechanism of a Nuclear Pore Assembly: A Molecular Biophysics View |
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Authors: | Vasily V Kuvichkin |
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Institution: | (1) Department of Mechanisms Reception, Institute of Cell Biophysics, Russian Academy of Sciences, 142290 Pushchino, Moscow region, Russia |
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Abstract: | The basic problem of nuclear pore assembly is the big perinuclear space that must be overcome for nuclear membrane fusion
and pore creation. Our investigations of ternary complexes: DNA–PC liposomes–Mg2+, and modern conceptions of nuclear pore structure allowed us to introduce a new mechanism of nuclear pore assembly. DNA-induced
fusion of liposomes (membrane vesicles) with a single-lipid bilayer or two closely located nuclear membranes is considered.
After such fusion on the lipid bilayer surface, traces of a complex of ssDNA with lipids were revealed. At fusion of two identical
small liposomes (membrane vesicles) <100 nm in diameter, a “big” liposome (vesicle) with ssDNA on the vesicle equator is formed.
ssDNA occurrence on liposome surface gives a biphasic character to the fusion kinetics. The “big” membrane vesicle surrounded
by ssDNA is the base of nuclear pore assembly. Its contact with the nuclear envelope leads to fast fusion of half of the vesicles
with one nuclear membrane; then ensues a fusion delay when ssDNA reaches the membrane. The next step is to turn inside out
the second vesicle half and its fusion to other nuclear membrane. A hole is formed between the two membranes, and nucleoporins
begin pore complex assembly around the ssDNA. The surface tension of vesicles and nuclear membranes along with the kinetic
energy of a liquid inside a vesicle play the main roles in this process. Special cases of nuclear pore formation are considered:
pore formation on both nuclear envelope sides, the difference of pores formed in various cell-cycle phases and linear nuclear
pore clusters. |
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