What type of sorting signal is expected for a protein that transcribes the nuclear genome?

What type of sorting signal is expected for a protein that transcribes the nuclear genome?

• A. A mannose-6-phosphate modification
• B. A signal sequence that is rich in basic amino acids
• C. A long signal sequence recognized by the signal recognition particle
• D. It has no sorting signal

Answer: (B)

For a protein that transcribes the nuclear genome, a signal sequence rich in basic amino acids is expected because these sequences are characteristic of nuclear localization signals (NLS). Proteins that need to access the nucleus have specific sequences recognized by transport receptors in the nuclear pore complex. These basic amino acid-rich signals facilitate their import into the nucleus. In contrast, other modifications or signals such as a mannose-6-phosphate modification are typically associated with signals for lysosomal targeting, while signal sequences recognized by the signal recognition particle pertain to protein translocation into the endoplasmic reticulum (ER) for secretion or membrane insertion. The option suggesting that the protein has no sorting signal is also not applicable because nuclear proteins do possess the requisite signals for active transport into the nucleus. Thus, the protein's requirement for an NLS makes the choice of a signal sequence rich in basic amino acids the most fitting answer.

For a protein that transcribes the nuclear genome, a signal sequence rich in basic amino acids is expected because these sequences are characteristic of nuclear localization signals (NLS). Proteins that need to access the nucleus have specific sequences recognized by transport receptors in the nuclear pore complex. These basic amino acid-rich signals facilitate their import into the nucleus.

In contrast, other modifications or signals such as a mannose-6-phosphate modification are typically associated with signals for lysosomal targeting, while signal sequences recognized by the signal recognition particle pertain to protein translocation into the endoplasmic reticulum (ER) for secretion or membrane insertion. The option suggesting that the protein has no sorting signal is also not applicable because nuclear proteins do possess the requisite signals for active transport into the nucleus. Thus, the protein's requirement for an NLS makes the choice of a signal sequence rich in basic amino acids the most fitting answer.