title: Transcriptional profile of ras1 and ras2 and the potential role of farnesylation in the dimorphism of the human pathogen Paracoccidioides brasiliensis.
abstract: Paracoccidioides brasiliensis is a thermo-dimorphic fungus that causes a human systemic mycosis with high incidence in Latin America. Owing to their participation in the control of pathogen morphogenesis, differentiation and virulence, it was decided to characterize ras genes in P. brasiliensis. ras1 and ras2 were identified to be coding for two different proteins with high identity. The ras transcriptional pattern was investigated by reverse transcription PCR (RT-PCR) during mycelium-to-yeast (M-->Y) transition, heat shock at 42 degrees C and after internalization of yeast cells by murine macrophages. Both genes were downregulated inside macrophages and ras1, at 42 degrees C. In contrast, ras genes did not show any transcriptional variation during the M-->Y transition. The fact that Ras proteins are attached to the membrane via farnesylation prompted the use of a farnesyltransferase inhibitor to investigate the importance of this process for vegetative growth and dimorphic transition. Farnesylation blockage interfered with the vegetative growth of yeast cells and stimulated germinative tube production even at 37 degrees C. During Y-->M transition, the inhibitor increased filamentation in a dose-dependent manner, indicating that impaired farnesylation favours the mycelium form of P. brasiliensis. The results suggest that ras genes might have a role in dimorphism, heat shock response and in host-pathogen interaction.
authors.affiliation: Departamento de Biologia Celular, Universidade de Brasília, Brasília, DF, Brazil.
authors.forename: Larissa
authors.initials: L
authors.lastname: Fernandes
authors.forename: Hugo C
authors.initials: HC
authors.lastname: Paes
authors.forename: Aldo H
authors.initials: AH
authors.lastname: Tavares
authors.forename: Simoneide S
authors.initials: SS
authors.lastname: Silva
authors.forename: Alessandra
authors.initials: A
authors.lastname: Dantas
authors.forename: Célia M A
authors.initials: CM
authors.lastname: Soares
authors.forename: Fernando A G
authors.initials: FA
authors.lastname: Torres
authors.forename: Maria Sueli S
authors.initials: MS
authors.lastname: Felipe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics*; D020869:Gene Expression Profiling; D006358:Hot Temperature; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008969:Molecular Sequence Data; D010228:Paracoccidioides / Q000166:cytology* / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny; D054876:Prenylation; D012331:RNA, Fungal / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger