Parts of ribosomes shift from cytosol to nucleus and from nucleus to cytoplasm: Is this true? If yes, why is it so?

Question

Piper Anderson · Accepted Answer

Ribosomal proteins are made in cytosol which then enter the nucleus through nuclear pores in case of eukaryotes. Inside the nucleus, ribosomal proteins are integrated with rRNA to form ribosomal subunits.

Each ribosome is made up of two subunits, and each subunit is made of rRNA and proteins. Ribosomal proteins are translated/synthesised in cytoplasm by other existing ribosomes from specific mRNAs. These ribosomal proteins must be integrated with another component of ribosome i.e. rRNA to form ribosomal subunits.

Assembly of ribosomal proteins and rRNA can happen within eukaryotic nucleus, at a location known as nucleolus. The genetic DNA transcripts rRNA within nucleus and integration of ribosomal proteins with rRNA takes place nearby. The factory of integration where ribosomal subunits are generated appear as nucleolus within nucleus.

Nuclear membrane in eukaryotes is associated with pores through which ribosomal proteins can enter nucleus from cytosol and pores also allow ribosomal subunits to come out in cytoplasm.

Proteins which are delivered in the lumen of endoplasmic reticulum are meant for other membrane bound organelles or are secretory products of the cell.

Benjamin Alvin · Answer

undefined The small ribosomal subunit is assembled in the nucleus and then transported to the cytoplasm, where it combines with the large ribosomal subunit to form a functional ribosome. This process ensures proper functioning of the cell and effectively regulates protein synthesis. Yes, it is true that ribosomal subunits shift between the cytosol and the nucleus.

Hudson Ansley · Answer

undefined Yes, it is true that parts of ribosomes can shift between the cytosol and the nucleus. This movement is facilitated by various mechanisms within the cell. Ribosomes are essential cellular organelles responsible for protein synthesis. The process of protein synthesis involves both the transcription of messenger RNA (mRNA) in the nucleus and the translation of mRNA into proteins in the cytosol.

Ribosomal RNA (rRNA) is synthesized in the nucleolus, a substructure within the nucleus. Once synthesized, the rRNA combines with ribosomal proteins to form ribosomal subunits, which are then exported from the nucleus to the cytoplasm. In the cytoplasm, these subunits come together to form functional ribosomes capable of protein synthesis.

However, certain conditions or cellular processes may necessitate the movement of ribosomal components back into the nucleus. For example, in response to cellular stress or specific signals, ribosomal proteins may undergo nucleocytoplasmic shuttling, where they are imported back into the nucleus. This movement allows for the regulation of ribosome biogenesis and protein synthesis in the cell.

Additionally, ribosomal components such as ribosomal proteins and ribosome assembly factors play roles in various nuclear processes beyond ribosome assembly, including DNA repair, regulation of gene expression, and cell cycle control. Therefore, the dynamic movement of ribosomal components between the cytosol and the nucleus is crucial for maintaining cellular homeostasis and ensuring proper cellular functions.