Expression of a constitutively active Ca super(2+)/calmodulin-dependent kinase in Aspergillus nidulans spores prevents germination and entry into the cell cycle

• Published in: The Journal of biological chemistry Vol. 272; no. 6; pp. 3223 - 3230
• Main Authors: Dayton, J S, Sumi, M, Nanthakumar, N N, Means, A R
• Format: Journal Article
• Language: English
• Published: 01.02.1997
• Subjects: Aspergillus nidulans
• ISSN: 0021-9258

The unique gene for Ca super(2+)/calmodulin-dependent protein kinase (CaMK) has been shown to be essential in Aspergillus nidulans. Disruption of the gene prevents entry of spores into the nuclear division cycle. Here we show that expression of a constitutively active form of CaMK also prevents spores from entering the first S phase in response to a germinating stimulus. Expression of the constitutively active kinase induces premature activation of NIME super(cyclin B)/NIMX super(cdc2) in G sub(0)/G sub(1). As NIMX super(cdc2) is present in spores, the elevation of maturation promotion factor activity may be secondary to the early production of NIME super(cyclin B) or post-translation modification of maturation promotion factor. The expression of the constitutively active CaMK also results in the appearance of NIMA kinase activity within 1 h of the germinating signal. These results support the contention that the activities of maturation promotion factor and NIMA are coincidentally regulated in A. nidulans and suggest that the unscheduled appearance of one or both of these activities may be sufficient to prevent A. nidulans spores from entering into DNA synthesis.