No abstract

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac109 core gene has been previously characterized as an essential late gene. Our results showed that budded virions could be detected in supernatants of infected Sf-9 cells, even when ac109 knockout viruses displayed a single-cell infection phenotype. Moreover, confocal microscopy analysis revealed that budded virions can enter the cytoplasm but are unable to enter the cell nucleus. This defect could be repaired by complementing ac109 in trans. In addition, polyhedra of normal size could be detected in Sf-9 nuclei infected with ac109 knockout viruses. However, electron microscopy demonstrated that these occlusion bodies were empty. Altogether, these results indicate that ac109 is required for infectivity of both phenotypes of virus.

Yeast cells can adapt their growth in response to the nutritional environment. Glucose is the favourite carbon source of Saccharomyces cerevisiae, which prefers a fermentative metabolism despite the presence of oxygen. When glucose is consumed, the cell switches to the aerobic metabolism of ethanol, during the so-called diauxic shift. The difference between fermentative and aerobic growth is in part mediated by a regulatory mechanism called glucose repression. During glucose derepression a profound gene transcriptional reprogramming occurs and genes involved in the utilization of alternative carbon sources are expressed. Protein kinase A (PKA) controls different physiological responses following the increment of cAMP as a consequence of a particular stimulus. cAMP-PKA is one of the major pathways involved in the transduction of glucose signalling. In this work the regulation of the promoters of the PKA subunits during respiratory and fermentative metabolism are studied. It is demonstrated that all these promoters are upregulated in the presence of glycerol as carbon source through the Snf1/Cat8 pathway. However, in the presence of glucose as carbon source, the regulation of each PKA promoter subunits is different and only TPK1 is repressed by the complex Hxk2/Mig1 in the presence of active Snf1. Copyright © 2017 John Wiley & Sons, Ltd.

The cAMP-dependent protein kinase (PKA) signaling is a broad pathway that plays important roles in the transduction of environmental signals triggering precise physiological responses. However, how PKA achieves the cAMP-signal transduction specificity is still in study. The regulation of expression of subunits of PKA should contribute to the signal specificity. Saccharomyces cerevisiae PKA holoenzyme contains two catalytic subunits encoded by TPK1, TPK2 and TPK3 genes, and two regulatory subunits encoded by BCY1 gene. We studied the activity of these gene promoters using a fluorescent reporter synthetic genetic array screen, with the goal of systematically identifying novel regulators of expression of PKA subunits. Gene ontology analysis of the identified modulators showed enrichment not only in the category of transcriptional regulators, but also in less expected categories such as lipid and phosphate metabolism. Inositol, choline and phosphate were identified as novel upstream signals that regulate transcription of PKA subunit genes. The results support the role of transcription regulation of PKA subunits in cAMP specificity signaling. Interestingly, known targets of PKA phosphorylation are associated with the identified pathways opening the possibility of a reciprocal regulation. PKA would be coordinating different metabolic pathways and these processes would in turn regulate expression of the kinase subunits.