Ribosomes are the cell’s protein synthesis machinery. Spliceosomes are the cell’s pre-mRNA (messenger Ribonucleic acid) processing machinery. Both of them have RNA as their key functional component. both of these structures are ribonucleoproteins that have enzyme activity.
The following structural similarities are observed between ribosomes and spliceosomes:
• Both these structures are made of ribonucleoproteins
• They assemble on their targets to form functional complexes. Ribosomes occur as individual subunits in the cytoplasm. Only during translation of proteins these two subunits assemble. Similarly, the subunits of spliceosome assemble only during splicing or pre-mRNA (messenger Ribonucleic acid)
• The catalytic activity of both of these macromolecules resides in their RNA components and not in their protein components. Spliceosomes have snRNA (small nuclear RNA) which catalyze the removal of introns. Similar role is played by rRNA (ribosomal RNA) in catalysis of formation of peptide bond between amino acids during protein synthesis
Ribosomes and spliceosomes support the RNA world theory due to the enzymatic activity their RNA possess, ability to splice them self (many introns have self-splicing activity), and their ability to form the genetic material (several virus have RNA as their genetic material). These molecules can serve the purpose of enzymes and genetic material. Hence, many scientists argue that primitive world was RNA world.