CLONING AND CHARACTERIZATION OF A CDNA CODING FOR CANDIDA-ALBICANS POLYUBIQUITIN

Immunoscreening of a Candida albicans cDNA library in the expression v ector lambda gt11 with rabbit polyclonal antibodies against the 37 kDa cell surface laminin receptor of C. albicans resulted in the isolatio n of a cDNA clone of 0.9 kb. Sequencing of this clone demonstrated a f ull length open reading frame encoding the polyubiquitin, which contai ns three tandem copies, head-to-tail spacerless repeats, of the 228 nu cleotides coding for the 76 amino acids of the ubiquitin protein, whic h is identical to that of Saccharomyces cerevisiae. The third copy pos sesses an extra C-terminal amino acid which is distinct to that found in S. cerevisiae. Northern blot analysis revealed a single mRNA popula tion of about 1 kb present in similar amounts in both yeast and myceli al cells. This indicates that the C. albicans polyubiquitin gene (UBI1 ) encodes a polyubiquitin precursor protein containing three ubiquitin repeats. Immunofluorescence and Western immunoblotting experiments wi th polyclonal antibodies against mammalian ubiquitin suggest the prese nce of ubiquitinated protein moieties in the wall of C. albicans cells .