PINA Is Essential for Growth and Positively Influences NIMA Function in Aspergillus nidulans

Abstract

The phospho-Ser/Thr-directed prolyl-isomerase Pin1 was originally identified in vertebrate systems as a negative regulator of NIMA, a Ser/Thr protein kinase that regulates the G 2 /M transition in Aspergillus nidulans. Here we explore the physiological roles of the Pin1 orthologue, PINA, in A. nidulans and evaluate the relevance of the interaction of PINA with NIMA in this fungus. We find pinA to be an essential gene in A. nidulans. In addition, when PINA levels are reduced 50-fold the cells grow at a reduced rate. Upon germination under conditions that repress PINA expression, the cells are delayed in the interphase activation of NIMX cdc2 , whereas they traverse the other phases of the cell cycle at a similar rate to controls. These results indicate that a marked reduction of PINA results in a lengthening of G 1 . Additionally, PINA repression increases the rate at which the cells enter mitosis following release from a hydroxyurea arrest without altering the sensitivity of the fungus to agents that activate the replication or DNA damage checkpoints. In contrast to predictions based on Pin1, the physical interaction between PINA and NIMA is primarily dependent upon the prolylisomerase domain of PINA and the C-terminal 303 amino acids of NIMA. Finally, reduction of PINA levels exacerbates the nimA5 temperature-sensitive mutant, whereas overexpression of PINA decreases the severity of this mutation, results that are consistent with a positive genetic interaction between PINA and NIMA. Thus, although PINA is essential and positively regulates NIMA function, A. nidulans is most sensitive to a reduction in PINA concentration in G 1 rather than in G 2 /M.

Analysis of All Protein Phosphatase Genes in Aspergillus nidulans Identifies a New Mitotic Regulator, Fcp1

“…Pin1 has been shown to both inhibit Fcp1 and activate Cdk1, thus promoting mitotic hyperphosphorylation of RNAP II CTD. It will thus be interesting to investigate the potential role of Pin1 (PinA in A. nidulans [20]) in mediating the genetic interactions and mitotic phenotypes (see below) we have uncovered while studying Fcp1 and Cdk1. One prediction is that increased expression of PinA might phenocopy the fcp1 ts cdk1F double mutant (by inhibiting Fcp1 and activating Cdk1).…”

Structure and function of the human parvulins Pin1 and Par14/17

“…Knockdown/Knockout of hPin1 in fast dividing cells, such as cancer cells, leads to mitotic arrest and apoptosis (Lu et al, 1996;Rippmann et al, 2000), while addition of Pin1 to Xenopus extracts or overexpression in human cell lines leads to inhibition of G2/M transition (Lu et al, 1996;Crenshaw et al, 1998;Shen et al, 1998). Despite its unique role in the cell cycle, Pin1 is not essential for survival in metazoan organisms (Maleszka et al, 1996;Fujimori et al, 1999;Liou et al, 2002), while it is crucial for most representatives of unicellular unikonts such as the ascomycetes, saccharomyces, candida and aspergillus/emericella (Hanes et al, 1989;Lu et al, 1996;Devasahayam et al, 2002;Joseph et al, 2004).…”

Role of Ess1 in Growth, Morphogenetic Switching, and RNA Polymerase II Transcription in Candida albicans

“…Homologs of Ess1 are found in all major pathogenic fungi that have been examined, including C. albicans [52], Candida glabrata (REFSEQ XP_445146), Cryptococcus neoformans [53], and Aspergillus nidulans (PinA) [54]. In C. albicans and A. nidulans Ess1 (PinA) is essential for growth [52], [54].…”

“…In C. albicans and A. nidulans Ess1 (PinA) is essential for growth [52], [54]. In Cryptococcus neoformans , Ess1 is not essential for growth, but is required for expression of virulence factors melanin and urease and for virulence in a mouse model [53].…”