Candida albicans is the most prominent opportunistic fungal pathogen in humans. Multiple factors are associated with the virulence of C. albicans, including morphogenesis, cell wall organization and growth rate. Here, we describe the identification and functional characterization of CaECM25, a gene that has not been reported before. We constructed Caecm25?/? mutants and investigated the role of the gene in morphogenesis, cell wall organization and virulence. CaECM25 deletion resulted in defects in cell separation, a slower growth rate, reduced filamentous growth and attenuated adherence to plastic surfaces. The Caecm25?/? mutant was also significantly less virulent than wild type when tested for systemic infection in mice. Therefore, CaECM25 plays important roles in morphogenesis, cell wall organization and virulence.
As a newly identified transcription factor in Candida albcians, CaSfl1 has been shown to be involved in cell flocculation and filamentation and in the negative regulation of several genes involved in hyphal growth. In this study, we constructed Casfl1△/△ mutants and confirmed that deletion of this gene indeed affected cell flocculation and filamentation. In addition, by RT-PCR we found that while Casfl1 repressed the expression of several hypha-specific genes including HWP1, ECE1, ALS1, ALS3, and FLO8, it strongly activated the expression of the heat-shock protein genes HSP30 and HSP90 under certain stress conditions. Therefore, we propose that CaSfl1 can act as both positive and negative regulators, thereby playing a dual role in transcriptional controls in Candida albicans.
Eukaryotic flagella are microtubule based cellular organelles,which play pivotal roles in cell motility and ce...
Tian Piao,Liang Wang,Min-na Luo,Mu-qing Cao,Jun-min Pan~* Protein Science Laboratory of the Ministry of Education,School of Life Sciences,Tsinghua University,Beijing 100084, China
DNA polymerase delta is encoded by the POLD1 gene,the transcription of which is strictly cell cycle-dependent.However,the means by which POLD1 transcription is regulated by the cell cycle mechanism is currently unknown.We discovered a novel element in the POLD1 promoter known as a CDE(cell cycle-dependent element)/CHR(cell cycle gene homology region) element.A series of luciferase reporter constructs containing various POLD1 promoter mutations were used to investigate the role of the CDE/CHR element in POLD1 transcription.When the CDE/CHR element was mutated,the promoter activity was up-regulated,and the cell-cycle related factors E2F1 and p21 stopped regulating the promoter.Furthermore,cell cycle-dependent changes in the promoter activity required the integrative CDE/CHR element.Electrophoretic mobility shift assay(EMSA) revealed the presence of at least three types of DNA/protein complexes binding to the CDE/CHR element.Our findings provide strong evidence that the CDE/CHR-like sequence is an active functional element in the POLD1 promoter,which is important for the cell cycle regulation of the POLD1 gene.
SONG NanMeng1,ZHU XiaoYu1,2,SHI Lei1,AN Jing1,WU YanWei1 & SANG JianLi1 1 Key Laboratory of Cell Proliferation and Regulation of Ministry of Education,Beijing Normal University,Beijing 100875,China
