Evolutionary conservation of a testes-specific proteasome subunit gene in Drosophila.
Proteasomes are large multisubunit particles that act as the proteolytic machinery for the ubiquitin-dependent proteolytic pathway. The core of this complex, the 20S proteasome, is made up of seven alpha-type and seven beta-type subunits, arranged in an (alpha1-alpha7)(beta1-beta7)(beta1-beta7)(alpha1-al pha7) configuration. Previous work had shown that there exist alternative isoforms of the Drosophila melanogaster alpha4-type subunit, encoded by two distinct genes, alpha4t1_dm and alpha4t2_dm, and that these are expressed exclusively in the germline of the testes. We sought to investigate the evolutionary conservation of this phenomenon by screening for orthologs of the alpha4-type gene family in the distantly related Drosophila species, D. virilis. We isolated the D. virilis orthologs of the somatically expressed gene, alpha4_dm, and the testes-specific gene, alpha4t2_dm. We failed to find an ortholog of the other testes-specific gene, alpha4t1_dm. The alpha4_dv gene maps to the X chromosome at 12A-C, its product shares 90% amino acid identity with alpha4_dm, and it is expressed at high levels in both males and females. The other gene, alpha4t_dv, encodes a protein most similar to the testes-specific alpha4t2_dm proteasome subunit (59% a.a. identity), and it maps to position 27 on chomosome 2. The expression of the alpha4t_dv gene is testes-specific, like that of alpha4t2_dm. The existence of testes-specific alpha4-type subunits in two widely diverged subgenera of Drosophila suggests that these subunit isoforms have important functional roles in spermatogenesis.
Belote
J M
JM
Department of Biology, Syracuse University, 130 College Place, Syracuse, NY 13244, USA. jbelote@mailbox.syr.edu
Miller
M
M
Smyth
K A
KA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000235:genetics*; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004330:Drosophila / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D029721:Drosophila Proteins; D019143:Evolution, Molecular; D015870:Gene Expression / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D017344:Genes, Insect / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012737:Sex Factors; D013737:Testis / Q000201:enzymology*
D029721:Drosophila Proteins; D009097:Multienzyme Complexes; D011506:Proteins; C113984:alpha4t-DV protein, Drosophila; D004247:DNA; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex