Arrange the steps required for presentation of epitopes by class I MHC molecules in chronological order, with the earliest step at the top.
1. Proteasomes digest intracellular antigenic proteins
2. transport proteins translocate the short peptide fragments from the cytoplasm into the endoplasmic reticulum (ER)
3. class I MHC molecules are assembled and loaded with a peptide fragments
4. class I MHC molecule/peptide fragments are carried to and anchored in the plasma membrane