Requirement for lamin B receptor and its regulation by importin {beta} and phosphorylation in nuclear envelope assembly during mitotic exit.
Lamin B receptor (LBR), a chromatin and lamin B-binding protein in the inner nuclear membrane, has been proposed to target the membrane precursor vesicles to chromatin mediated by importin β during the nuclear envelope (NE) assembly. However, the mechanisms for the binding of LBR with importin β and the membrane targeting by LBR in NE assembly remain largely unknown. In this report, we show that the amino acids (aa) 69-90 of LBR sequences are required to bind with importin β at aa 45-462, and the binding is essential for the NE membrane precursor vesicle targeting to the chromatin during the NE assembly at the end of mitosis. We also show that this binding is cell cycle-regulated and dependent on the phosphorylation of LBR Ser-71 by p34(cdc2) kinase. RNAi knockdown of LBR causes the NE assembly failure and abnormal chromatin decondensation of the daughter cell nuclei, leading to the daughter cell death at early G(1) phase by apoptosis. Perturbation of the interaction of LBR with importin β by deleting the LBR N-terminal spanning region or aa 69-73 also induces the NE assembly failure, the abnormal chromatin decondensation, and the daughter cell death. The first transmembrane domain of LBR promotes the NE production and expansion, because overexpressing this domain is sufficient to induce membrane overproduction of the NE. Thus, these results demonstrate that LBR targets the membrane precursor vesicles to chromatin by interacting with importin β in a LBR phosphorylation-dependent manner during the NE assembly at the end of mitosis and that the first transmembrane domain of LBR promotes the LBR-bearing membrane production and the NE expansion in interphase.
Lu
Xuelong
X
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Shi
Yang
Y
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Lu
Quanlong
Q
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Ma
Yan
Y
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Luo
Jia
J
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Wang
Qingsong
Q
State Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
Ji
Jianguo
J
State Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing 100871, China.
Jiang
Qing
Q
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China.
Zhang
Chuanmao
C
From the The Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education and the State Key Laboratory of Bio-membrane and Membrane Bio-engineering, Beijing 100871, China. Electronic address: zhangcm@pku.edu.cn.
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D005260:Female; D016193:G1 Phase / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008938:Mitosis / Q000502:physiology*; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*; D000097682:Lamin B Receptor
D002843:Chromatin; D018160:Receptors, Cytoplasmic and Nuclear; D028961:beta Karyopherins; D000097682:Lamin B Receptor