Functional and genetic interactions of Ribosomal-like Protein 24
Nearly all the processes within a cell are mediated by proteins: metabolism, movement, growth, and even death. These proteins are generated by a type of intracellular machinery called the ribosome which translates the cell’s genetic code into a functional protein. But where and how are ribosomes generated? Current research indicates that ribosomes are first made into two separate parts near the genetic material stored in the cell’s nucleus. The new subunits are passed through a discriminating gateway called the Nuclear Pore Complex (NPC) that separates the nucleus from the remainder of the cell’s interior, or cytoplasm. The ribosomes are very large, however, and cannot pass through the NPC on their own. It has been found that some proteins function to “chaperone” the ribosomal subunits out of the nucleus by assisting interaction between the ribosome and the NPC. We suspect a certain protein in yeast, Ribosomal-like Protein 24 (Rlp24), is involved in this export pathway. Its specific function is not yet known, but it has been previously determined that it binds to the ribosome in the nucleus and then is unloaded in the cytoplasm. In order to determine if this protein has a role in ribosome export, several genetic and functional tests were performed. In the first experiment, an altered form of Rlp24 with a molecular tag was expressed in cells that are deficient in specific proteins that comprise the Nuclear Pore Complex. A change in growth with these mutations suggests a functional interaction between the two proteins. Next, a screen for a gene that would restore normal growth in these mutants was done, suggesting that any of the potential genes also interact in the pathway. Finally, a special screen called a Yeast Two-Hybrid assay was used to identify proteins that actually bind to and function with Rlp24. From this series of tests, it was determined that Rlp24 does in fact interact functionally with specific components of the Nuclear Pore Complex, several of which have previously been identified as interacting in known export pathways. Additionally, the other screens identified one novel genetic interaction as well as two functional interactors with Rlp24. Though one physical interactor, a protein called Nog1, has already been cited in literature, the role of the other interactors in export and their relationships with Rlp24 are not yet known. However, the information gathered highly suggests that Rlp24 has a role in export and provides a basis for further testing and characterization.