Identification of the goldfish 20S proteasome beta 6 subunit bound to nuclear matrix

Proteasomes are large, multisubunit particles that act as the proteolytic m achinery for most of the regulated intracellular protein breakdown in eukar yotic cells. Proteasomes are present in both the nucleus and cytoplasm. Whe n ne analyzed the molecular composition of protein constituents of the nucl ear matrix preparation of goldfish oocytes by two-dimensional polyacrylamid e gel electrophoresis followed by sequence anal! sis, ne found a 26 kDa spo t identical in amino acid sequence to the beta 6 subunits of the 20S protea some, No spot of other subunits of 20S proteasome was detected, Here we des cribe the cloning, sequencing and expression analysis of Carassius auratus, beta 6_ca, which encodes one of the proteasome beta subunits from goldfish ovary. From the screening of an ovarian cDNA library, two types of cDNA we re obtained, one 941 bp and the other 884 bp long, The deduced amino acid s equences comprise 239 and 238 residues, respectively. These deduced amino a cid sequences are highly homologous to those of beta 6 subunits of other ve rtebrates. Immunoblot analysis of nuclear matrix using anti-proteasome anti bodies showed only a spot of beta 6_ca, These results suggest that the beta 6 subunit of the goldfish 20S proteasome, beta 6_ca, is responsible for an choring proteasomes in the nucleus. (C) 2000 Federation of European Biochem ical Societies.