The nucleolus doesn't directly contribute to protein synthesis. Instead, it plays a crucial role in producing ribosomes, which are the cellular machinery responsible for protein synthesis. Here's how:

1. Ribosomal RNA (rRNA) synthesis: The nucleolus is the site of rRNA synthesis, which is a key component of ribosomes.

2. Ribosomal subunit assembly: The nucleolus assembles rRNA with ribosomal proteins, imported from the cytoplasm, to form the two subunits of ribosomes: the small subunit (40S) and the large subunit (60S).

3. Export of subunits: These subunits are then exported from the nucleus through nuclear pores to the cytoplasm, where they join to form functional ribosomes.

In summary: The nucleolus is like a factory for ribosomes. It produces the rRNA and assembles it with ribosomal proteins, creating the ribosomes that are essential for protein synthesis.