Ms. Clark et al., Identification and characterization of a beta proteasome subunit cluster in the Japanese pufferfish (Fugu rubripes), J IMMUNOL, 165(8), 2000, pp. 4446-4452
The low molecular mass polypeptide (LMP2, LMP7, and MECL-1) genes code for
beta-type subunits of the proteasome, a multimeric complex that degrades pr
oteins into peptides as part of the MHC class I-mediated Ag-presenting path
way. These gene products are up-regulated in response to infection by IFN-g
amma and replace the corresponding constitutively expressed subunits (X, Y,
and Z) during the immune response. In humans, the LMP2 and LMP7 genes both
reside within the class II region of the MHC (6p21.3), while MECL-1 is loc
ated at 16q22.1. In the present study, we have identified all three IFN-gam
ma-regulated beta-type proteasome subunits in Fugu, which are present as a
cluster within the Fugu MHC class I region. We show that in this species, L
MP7, LMP2, and MECL-1 are linked. Also within this cluster is an LMP2-like
subunit (which seems specific to all teleosts tested to date) and a closely
linked LMP7 pseudogene, indicating that within Fugu and potentially other
teleosts, there has been an additional regional duplication involving these
genes.