What are the two main functions of nuclear envelope?

Answer 1

The nuclear envelope is a double membrane structure surrounding the nucleus. Its function is to provide compartmentalization to regulate the movement of materials in and out of the cell, and to provide structural support of the nucleus.

Answer 2

According to a site I just visited, these are the function of nuclear envelope:

Functions of nuclear envelope proteins during development
The nuclear envelope separates the nucleoplasm from the cytoplasm and is composed of three structural components: the outer and inner nuclear membranes, the nuclear pore complexes, and the proteinaceous layer underneath the inner nuclear membrane, called the nuclear lamina. The lamina is mainly composed of intermediate filament proteins A and B type lamins, and is associated with the inner nuclear membrane, partly through interacting with integral proteins of the inner nuclear membrane. A growing list of these integral membrane proteins have been identified, among which are the LEM domain proteins including LAP2, Emerin and MAN1. Many functions have been attributed to the nuclear lamina and its associated proteins, such as chromatin organization, nuclear assembly, DNA replication, transcription and others. Interestingly, mutations in lamin and lamin-associated inner nuclear membrane proteins (such as emerin, MAN1 and LBR) have been found to cause a number of genetic diseases in humans, such as muscular dystrophies, lipodystrophy, neuropathy, and pre-mature aging. Uncovering the molecular mechanisms underlying these diseases requires a better understanding of the functions of these nuclear envelope proteins in various developmental processes.

We are using C. elegans as a model system to study the in vivo functions of lamin and lamin-associated nuclear envelope proteins during development. The C. elegans nuclear envelope is similar to human nuclear envelopes: it contains lamin and a number of lamin-associated proteins (such as emerin and MAN1) and it undergoes cell cycle dependent assembly/reassembly. But the C. elegans nuclear envelope has a much simpler composition than human nuclear envelopes: many proteins encoded by multiple genes in humans have a single counterpart in C. elegans (Liu et al, 2000; Lee et al, 2000). Thus functional studies of nuclear envelope proteins are much easier in C. elegans. By studying the functions of C. elegans nuclear envelope proteins, we hope to better understand the molecular mechanisms underlying nuclear envelope-associated human diseases.

1. Ce-lamin/LMN-1 is essential for nuclear organization, cell cycle progression, and spatial organization of nuclear pore complexes

C. elegans has a single lamin gene, lmn-1. Its gene product, Ce-lamin/LMN-1, is present in both the interior and the periphery of all nuclei except for sperm (Liu et al, 2000). Using RNAi, we showed that lmn-1 is an essential gene that is required for maintaining nuclear shape, for proper organization of chromatin and correct spacing of nuclear pore complexes, and for normal cell cycle progression (Liu et al, 2000). We further showed that Ce-lamin is required for the proper localization of several nuclear envelope proteins, including Ce-emerin, Ce-MAN1 and UNC-84 (Gruenbaum et al, 2002; Lee et al, 2002; Liu et al, 2003). We are currently determining how Ce-lamin/LMN-1 exerts its multiple functions at the nuclear envelope.

2. Ce-emerin/EMR-1 and Ce-MAN1/LEM-2 have overlapping functions essential for proper chromosome segregation and cell division

Emerin and MAN1 are two LEM domain containing integral membrane proteins of the vertebrate nuclear envelope. Mutations in emerin cause X-linked recessive Emery-Dreifuss muscular dystrophy (EDMD), whereas the function of MAN1 is not known. Both emerin and MAN1 are conserved in C. elegans (encoded by emr-1 and lem-2 respectively). Animals lacking Ce-emerin/EMR-1 have no obvious defects (Gruenbaum et al, 2002). Removal of ~90% of Ce-MAN1/LEM-2 causes only 10-15% embryonic lethality. Interestingly, reducing the level of Ce-MAN1/LEM-2 in the absence of Ce-emerin/EMR-1 result in 100% embryonic lethality (Liu et al, 2003). The most striking phenotypes observed in these embryos are the presence of anaphase bridges and abnormally condensed chromatin, even during the first few cell divisions. These results demonstrate that Ce-emerin/EMR-1 and Ce-MAN1/LEM-2 have overlapping functions essential for proper chromosome segregation and cell division. We further show that these two proteins are required for the proper localization of Ce-lamin/LMN-1 and BAF-1, the C. elegans LEM domain binding protein (Liu et al, 2003). Our findings suggest the existence of a lamin-LEM domain protein-BAF-dependent pathway involved in regulating chromatin organization and cell cycle progression (Margalit et al, 2005). They also raise an intriguing possibility that other LEM domain proteins might protect tissues not affected in X-EDMD patients against the loss of emerin. We are currently studying how Ce-emerin and Ce-MAN1 function to allow proper chromosome segregation and cell division.

3. The nuclear architecture undergoes age-related changes in C. elegans

Mutations in lamins cause premature aging syndromes in humans, including the Hutchinson-Gilford Progeria Syndrome (HGPS) and Atypical Werner Syndrome. It has been shown that HGPS cells in culture undergo age-dependent progressive changes in nuclear architecture. However, it is unknown whether similar changes in nuclear architecture occur during the normal aging process. We have observed that major changes of nuclear architecture accompany C. elegans aging (Haithcock et al, 2005). We found that the nuclear architecture in most nonneuronal cell types undergoes progressive and stochastic age-dependent alterations, such as changes of nuclear shape and loss of peripheral heterochromatin. Furthermore, we show that the rate of these alterations is influenced by the insulin/IGF-1 like signaling pathway and that reducing the level of lamin and lamin-associated LEM domain proteins leads to shortening of lifespan. Our work not only provides evidence for changes of nuclear architecture during the normal aging process of a multicellular organism, but also suggests that HGPS is likely a result of acceleration of the normal aging process. Because the nucleus is vital for many cellular functions, our studies raise the possibility that the nucleus is a prominent focal point for regulating aging. We are currently investigating the molecular basis underlying these age-related nuclear architecture changes. Hope your question was cleared with this article. :)