Identification and linkage of the proteasome activator complex PA28 subunit genes in zebrafish.
PA28 is an activator of the latent 20S proteasome, a large multisubunit complex involved in intracellular proteolysis. Two forms of hexameric PA28 have been identified, PA28-(alphabeta)3 and PA28-(gamma)6, of which the former is of immunological importance. Both the PA28-alpha and PA28-beta subunits are inducible by interferon-gamma (IFN-gamma) and the PA28-(alphabeta)3 complex enhances the ability of the 20S proteasome to produce peptides suited for binding to major histocompatibility complex (Mhc) class I molecules. To identify the homologues of the PA28 subunits in zebrafish we screened a cDNA library and obtained full-length cDNA sequences of the genes PSME1, PSME2 and PSME3 coding for the PA28-alpha, PA28-beta and PA28-gamma subunits, respectively. Phylogenetic analysis indicates the existence of the ancestors of all three genes prior to the divergence of tetrapods and bony fishes. The IFN-gamma-inducible subunits, PA28-alpha and PA28-beta, evolve faster than the presumably older PA28-gamma subunit. Using zebrafish radiation hybrid panels, the genes PSME2 and PSME3 were mapped to linkage group 12 and shown to be separated by a distance of less than 2.4 cM. This observation suggests that an intrachromosomal duplication event created the precursor of the IFN-gamma-inducible genes from a PA28-gamma-like ancestor prior to their recruitment into the Mhc class I peptide presentation pathway.
Murray
B W
BW
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Corrensstrasse 42, 72076 Tübingen, Germany.
Sültmann
H
H
Klein
J
J
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000302:isolation & purification; D008040:Genetic Linkage / Q000235:genetics*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D005810:Multigene Family; D011506:Proteins / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D016415:Sequence Alignment; D015027:Zebrafish; D029961:Zebrafish Proteins
D009097:Multienzyme Complexes; D011506:Proteins; D029961:Zebrafish Proteins; C490051:psme1 protein, zebrafish; C490053:psme2 protein, zebrafish; C490054:psme3 protein, zebrafish; D003546:Cysteine Endopeptidases