Nuclear pore formation but not nuclear growth is governed by cyclin-dependent kinases (Cdks) during interphase

Abstract

Nuclear volume and the number of nuclear pore complexes (NPCs) on the nucleus almost double during interphase in dividing cells. How these events are coordinated with the cell cycle is poorly understood, particularly in mammalian cells. We report here, based on newly developed techniques for visualizing NPC formation, that cyclin-dependent kinases (Cdks), especially Cdk1 and Cdk2, promote interphase NPC formation in human dividing cells. Cdks seem to drive an early step of NPC formation because Cdk inhibition suppressed generation of 'nascent pores', which we argue are immature NPCs under the formation process. Consistent with this, Cdk inhibition disturbed proper expression and localization of some nucleoporins, including Elys/Mel-28, which triggers postmitotic NPC assembly. Strikingly, Cdk suppression did not notably affect nuclear growth, suggesting that interphase NPC formation and nuclear growth have distinct regulation mechanisms.

Nuclear size, nuclear pore number and cell cycle

“…[3][4][5][6][7] To address this question, we established novel techniques to study nuclear volume and NPC formation, and investigated how they were regulated during interphase in dividing human cells. 8,9 Our results indicate that Cdks, especially Cdk1 and Cdk2, control NPC formation during interphase. 9 Cdk inhibition suppressed the generation of the "nascent pores," which are immature NPCs in the process of forming and interrupted expression and localization of some nucleoporins.…”

“…8,9 Our results indicate that Cdks, especially Cdk1 and Cdk2, control NPC formation during interphase. 9 Cdk inhibition suppressed the generation of the "nascent pores," which are immature NPCs in the process of forming and interrupted expression and localization of some nucleoporins. Surprisingly, we also demonstrated that Cdk inhibition did 10 When we used Nup62-YFPexpressing cells, the NPC acceptor nuclei acquired Nup62-YFP signals without interphase NPC formation, likely due to the rapid turnover of Nup62-YFP within NPCs (Maeshima K, et al unpublished).…”

“…3) in the G 1 /S phase of HeLa cells, but not in roscovitine-treated cells. 9 Recently, using baby hamster kidney tsBN2 cells, a temperature-sensitive mutant of RCC1, we established a system allowing the inhibition or initiation of interphase NPC formation by changing the temperature. 8 In this system, interphase NPC formation actively occurs at permissive temperature (32°C), but not at non-permissive temperature (39.7°C) cells.…”

Diffusion through thin membranes: Modeling across scales

“…(15) to a distribution function f i (r) if r was located in the segmented nucleus (cytoplasm) and an adjacent point r + δrê i was located on the other side of the membrane in the segmented cytoplasm (nucleus). The permeability of the envelope was assumed to be uniform, since the density of the nuclear pores is high and they are rather uniformly located over the nuclear envelope [27,28]. Furthermore, the permeability was assumed to be constant during the simulation, since the total simulated time (only a few seconds) was short.…”

“…Using the solubility-diffusion model (see Introduction), P = KD m /w, together with equation A pore = K/n, where A pore is the cross-sectional area of one nuclear pore channel and n is the area density of the nuclear pores, we calculated a rough estimate for the effective nuclear pore diameter. The value D m that we used was the average of the nucleus and cytoplasm diffusion coefficients that we determined (21 μm 2 /s) and the value of n was the average of values from [27,28] (25 μm −2 ) and w ∼ 65 nm [29,30]. This way we obtained the effective nuclear pore area A pore ∼ 62 nm 2 , or effective pore diameter d pore ∼ 8.9 nm, which is in good agreement with experimental data [31,32].…”