Complete nucleotide sequence of Candida albicans 5.8S rRNA coding gene and flanking internal transcribed spacers.

Repeated sequences, like the 5.8S rRNA and its flanking regions in C. albicans, can be of particular interest as PCR targets; this is especially true if variations in sequence or length of these regions occur between members of a same genus or species (1). We therefore cloned ribosomal repetitive units of two C. albicans strains and determined the sequence of their respective Internal Transcribed Spacers (ITS) and 5.8S rRNA. This was achieved by using the Sequenase procedure (USB) with four different primers, one located in the 18S rRNA (sense, 1702-1727), one located in the 25S rRNA (antisense, 91 -109), and two located in the 5.8S rRNA (sense, 32-49; antisense 141-158). The 5' and 3' ends of the region encoding the 5.8S rRNA were identified by comparison with the equivalent gene from closely related fungi (2, 3). The length of this region encoding the 5.8S rRNA in C.albicans is 158 bp. The two ITS (ITS 1 and 2) located between 18S and 5.8S and 5.8S and 25S rRNA are respectively 138—139 bp, depending on the strain, and 151 bp long. Only three mismatches were observed between the sequence from the two C.albicans strains, one in the 5.8S rRNA coding gene and two in ITS 1. We found that the 5.8S rRNA of C.albicans is very closely related to those of other fungi like Saccharomyces cerevisiae (2) (95.0% homology), Schizosaccharomycespombe (3) (90.0% homology) and Neurospora crassa (4) (92.5% homology). In particular, nucleotides involved in the base pairing between the 5.8S rRNA and the 25S rRNA (5) are highly conserved. We have previously shown that these nucleotides involved in pairing are identical in the 25S rRNA of C.albicans and S. cerevisiae (6). This also holds true in the complementary 5.8S sequence except for one substitution in the 3 ' region of the 5.8S.