Saccharomyces cerevisiae strains display robust phenotypes in the presence of Dyskeratosis congenita mutations in the Cbf5 gene

Abstract

Dyskeratosis congenita is a rare, congenital disorder affecting the skin, nails and oral mucosa of patients that often progresses to bone marrow failure and an increased predisposition for a variety of carcinomas. Mutations in the human dyskerin gene have been identified as the most prevalent cause of the disease. Dyskerin is a pseudouridine synthase and the catalytic subunit of H/ACA ribonucleoproteins (RNPs) responsible for the modification of uridines to pseudouridine in ribosomal RNA (rRNA), but dyskerin also binds to the telomerase RNA component (TERC). Accordingly, Dyskeratosis congenita mutations have been reported to affect both telomerase function as well as ribosome biogenesis, but the relative contribution of each pathway to the diseases is under debate. As the yeast homolog of dyskerin, Cbf5, does not interact with telomerase RNA, Saccharomyces cerevisiae is an ideal model to identify the selective impact of Dyskeratosis congenita mutations on ribosome biogenesis. Therefore, chromosomal mutations in the yeast homologue of dyskerin, Cbf5, were introduced at positions corresponding to the mutations in human dyskerin that result in Dyskeratosis congenita. To determine if the mutations affect cellular fitness, we screened for growth defects in yeast. Growth curves at different temperatures and yeast spot assays under several stress conditions revealed that the mutations in cbf5 did not impair growth compared to wild type. These findings suggest that in the yeast cell, Dyskeratosis congenita mutations do not significantly affect ribosome biogenesis, and we discuss the implications for understanding the molecular cause of Dyskeratosis congenita.