Table of Contents
What moves molecules in and out of the cell nucleus?
The nuclear pore complex
The nuclear pore complex, a gateway into and out of the nucleus, is capable of an impressive feat: allowing large molecules to pass through, both selectively and quickly.
How do proteins enter the nucleus?
Nuclear protein import is a selective process. These short stretches of amino acids interact with proteins located in the cytoplasm, on the nuclear envelope, and/or at the nuclear pore complex. Following binding at the pore complex, proteins are translocated through the pore into the nucleus in a manner requiring ATP.
Which molecules are made in the cytoplasm and then transported into the nucleus?
RNA molecules, which are made in the nucleus, and ribosomal subunits, which are assembled there, are exported to the cytosol, while all the proteins that function in the nucleus are synthesized in the cytosol and are then imported.
What type of protein is transported into the nucleus?
Nuclear proteins are transported actively through nuclear pores by a selective, mediated process. The process is mediated by a nuclear localization signal (NLS), and can be divided into at least two steps, (a) targeting to the pores and (b) translocation through the pores.
How are molecules transported between the nucleus and the cytosol?
The Transport of Molecules between the Nucleus and the Cytosol The nuclear envelopeencloses the DNAand defines the nuclear compartment. This envelope consists of two concentric membranes that are penetrated by nuclear pore complexes (Figure 12-9).
How are mRNA proteins transported in the nucleus?
The mechanism of transport of mRNA-protein (mRNP) complexes from transcription sites to nuclear pores has been the subject of many studies. Using molecular beacons to track single mRNA molecules in living cells, we have characterized the diffusion of mRNP complexes in the nucleus.
When does the nuclear envelope of a cell disintegrate?
During mitosis, or cell division, the nuclear envelope disintegrates, but reforms as the two cells complete their formation and the chromatin begins to unravel and disperse. Nuclear Pores – The nuclear envelope is perforated with holes called nuclear pores.
What happens to the nucleolus during cell division?
During cell division, the nucleolus disappears. Some studies suggest that the nucleolus may be involved with cellular aging and, therefore, may affect the senescence of an organism. The Nuclear Envelope – The nuclear envelope is a double-layered membrane that encloses the contents of the nucleus during most of the cell’s lifecycle.