A Candida albicans gene encoding a novel DNA-binding protein that bound to the RPG box of Sacchammyces cerevisiae and the telomeric repeat sequence of C. albicans was previously cloned and designated RBFl (RPG-box-binding factor). In this report determination of the functional domains of the protein is described. The DNA-binding domain was 140 aa in length, was centrally located between two glutamine-rich regions, and correlated with transcriptional activation in S. cerevisiae. The results, together with the previous finding that showed its predominant localization in the nucleus, suggest that this DNA-binding protein could be a transcription factor. Disruption of the functional RBFl gene of C. albicans strains caused an alteration in cell morphology to the filamentous form on all solid and liquid media tested. Thus, we speculate that Rbflp may be involved in the regulation of the transition between yeast and filamentous forms at the level of transcription.

Electromobility shift assays with a DNA probe containing the Saccharomyces cerewisiae EN01 RPG box identified a specific DNA-binding protein in total protein extracts of Candida albicans. The protein, named Rbf 1 p (RPG-boxbinding protein 1), bound to other S. cerewisiae RPG boxes, although the nucleotide recognition profile was not completely the same as that of S. cerevisiae Rap1 p (repressor-activator protein l), an RPG-box-binding protein.The repetitive sequence of the C. albicans chromosomal telomere also competed with RPG-box binding to Rbflp. For further analysis, we purified Rbf 1 p 57 600-fold from C. albicans total protein extracts, raised mAbs against the purified protein and immunologically cloned the gene, whose ORF specified a protein of 527 aa. The bacterially expressed protein showed RPG-box-binding activity with the same profile as that of the purified one.The Rbflp, containing two glutamine-rich regions that are found in many transcription factors, showed transcriptional activation capability in S. cerewisiae and was predominantly observed in nuclei. These results suggest that R b f l p is a transcription factor with telomere-binding activity in C. albicans.

No abstract