ASCORBATE-DEPENDENT EXPRESSION OF UBIQUITIN GENES IN GUINEA-PIGS

In an attempt to characterize a gene(s), of which the expression is as corbate-dependent, a cDNA fragment encoding ubiquitin was isolated fro m a subtracted cDNA library constructed from spleen RNAs of ascorbate- deficient or -replete guinea pigs. On Northern blot analysis, three tr anscripts (1.8 kb ubiX, 1.3 kb ubiY and 0.7 kb ubiZ) were detected. Th e ubiY encodes four direct repeats of the 76 amino acid ubiquitin sequ ence with seven additional amino acids, V-Y-A-S-P-I-F, at the C-termin us. The transcript ubiX appears to comprise more than five repeats of the ubiquitin-encoding unit. The ubiZ encodes a ubiquitin monomer fuse d to an 80 amino acid extension exhibiting 100% amino acid sequence id entity to the human homolog, HUMUBA80R. The ubiX gene was expressed an imal-dependently. The ubiY mRNA levels decreased under ascorbate-defic ient conditions, and increased under ascorbate-replete conditions, whe reas ubiZ mRNA remained unaltered at low levels under the feeding cond itions used here. (C) 1997 Elsevier Science Ltd.