Alternative titles; symbols
HGNC Approved Gene Symbol: PSMB2
Cytogenetic location: 1p34.3 Genomic coordinates (GRCh38): 1:35,599,541-35,641,526 (from NCBI)
The proteasome is responsible for degradation of short lived and misfolded cytosolic and nuclear proteins in the cell. It consists of a complex of proteins that form a 20S core particle in both prokaryotes and eukaryotes. The 20S proteasome is composed of 7 alpha and 7 beta subunits that dimerize to form an alpha(7)beta(7)beta(7)alpha(7) structure. Subunits are designated alpha or beta depending on their homology to the Thermoplasma acidophilus proteasome in which the beta subunits are catalytically active. The 20S core complex associates with regulatory proteins that function as proteasome activators in vivo. One pathway of activation uses a 19S complex that is involved in the ubiquitin (191339) pathway of protein breakdown. The PA28 complex is an alternative proteasome activator that does not employ the use of ubiquitin. The complex is composed of 2 homologous subunits called alpha and beta, which form a hexameric ring. PA28 appears to be involved in the presentation of endogenous antigens by MHC class I molecules. The PA28 complex is expressed constitutively in antigen-presenting cells, and its expression is upregulated by interferon gamma (147570). Many of the genes involved in class I antigen presentation are encoded within the MHC, including the 2 proteasome subunits PSMB9 (177045), also known as LMP2, and PSMB8 (177046), also known as LMP7. McCusker et al. (1997) completed the mapping of the human proteasome beta-type genes: by fluorescence in situ hybridization they mapped the PSMB2 gene to 1p34.2, the PSMB3 gene (602176) to 2q35, and the PSMB4 gene (602177) to 1q21. They also showed that the genes encoding the alpha (600654) and beta (602161) subunits of the PA28 complex are closely linked on 14q11.2, within 1 Mb of the beta proteasome locus PSMB5 (600306). Thus, with the exception of the genes encoding the PSMB9 and PSMB8 subunits, the beta genes are not closely linked in the human genome. PSMB2 and PSMB4 map to regions of chromosome 1 that are proposed to be paralogous to regions of the human genome where other beta proteasome genes map: chromosome 6, containing the major histocompatibility complex, and chromosome 9.
McCusker, D., Jones, T., Sheer, D., Trowsdale, J. Genetic relationships of the genes encoding the human proteasome beta subunits and the proteasome PA28 complex. Genomics 45: 362-367, 1997. [PubMed: 9344661] [Full Text: https://doi.org/10.1006/geno.1997.4948]