A dihydrofolate reductase gene fromCandida albicans:molecular cloning

Primary structure of dihydrofolate reductase and mitochondrial ribosomal protein L36 genes from the basidiomycete Coprinus cinereus

We amplified and sequenced the dihydrofolate reductase (DHFR) gene of the basidiomycete Coprinus cinereus. Downstream of the DHFR coding region, a mitochondrial (mt) ribosomal protein L36 (RPL36) gene was discovered in the opposite orientation to DHFR gene. Putative polyadenylation signals of the two genes overlapped, both containing the 8-bp palindrome 5'-aatatatt-3'. The finding that C. cinereus DHFR gene is closely clustered with a mt protein gene strongly suggests that C. cinereus DHFR is closely related to mt function and evolution. The amino acid sequence of C. cinereus DHFR is most homologous to eukaryotic proteins such as Cryptococcus neoformans and Pneumocystis carinii DHFRs. However, the sequence of C. cinereus mt RPL36 closely resembles RPL36 of bacteria and cyanobacteria such as Synechocystis sp. and Escherichia coli. This result strongly supports the serial endosymbiotic theory of the development of ancestral eukaryotes, and suggests that C. cinereus mt RPL36 gene originated from the ancestral eubacterial genome.

Sequence of a dihydrofolate reductase-encoding gene from Candida albicans

The nucleotide (nt) sequence of the dihydrofolate reductase (DHFR)-encoding gene (DFR1) of Candida albicans was determined. The gene contains an open reading frame of 576 nt, coding for a protein of 192 amino acid (aa) residues (calculated M(r) 22,222), that is 38.5 and 31% similar to the Saccharomyces cerevisiae and human enzymes, respectively. The first 36 residues, at the N terminus, of the deduced aa sequence are identical to those determined by sequencing of the purified enzyme from C. albicans. Putative transcription start points were also determined. Restriction-fragment-length polymorphism analysis of the DFR1 chromosomal region suggests the presence of a single copy of the gene per haploid genome and shows a limited variability among the different C. albicans strains tested.