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Abedi, Majid (1)
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Transcriptional transactivation by selected short random peptides attached to lexA-GFP fusion proteins
BMC Molecular Biology
Transcriptional transactivation is a process with remarkable tolerance for sequence diversity and structural geometry. In studies of the features that constitute transactivating functions, acidity has remained one of the most common characteristics observed among native activation domains and activator peptides.
We performed a deliberate search of random peptide libraries for peptides capable of conferring transcriptional transactivation on the lexA DNA binding domain. Two libraries, one composed of C-terminal fusions, the other of peptide insertions within the green fluorescent protein structure, were used. We show that (i) peptide sequences other than C-terminal fusions can confer transactivation; (ii) though acidic activator peptides are more common, charge neutral and basic peptides can function as activators; and (iii) peptides as short as 11 amino acids behave in a modular fashion.
These results support the recruitment model of transcriptional activation and, combined with other studies, suggest the possibility of using activator peptides in a variety of applications, including drug development work.
A Fungal Kinesin Required for Organelle Motility, Hyphal Growth, and Morphogenesis
Turgeon, B. Gillian
Yoder, Olen C.
Wirsel, Stefan G.
Aist, James R.
Molecular Biology of the Cell
A gene (NhKIN1) encoding a kinesin was cloned from Nectria haematococca genomic DNA by polymerase chain reaction amplification, using primers corresponding to conserved regions of known kinesin-encoding genes. Sequence analysis showed that NhKIN1 belongs to the subfamily of conventional kinesins and is distinct from any of the currently designated kinesin-related protein subfamilies. Deletion of NhKIN1 by transformation-mediated homologous recombination caused several dramatic phenotypes: a 50% reduction in colony growth rate, helical or wavy hyphae with reduced diameter, and subcellular abnormalities including withdrawal of mitochondria from the growing hyphal apex and reduction in the size of the Spitzenkörper, an apical aggregate of secretory vesicles. The effects on mitochondria and Spitzenkörper were not due to altered microtubule distribution, as microtubules were abundant throughout the length of hyphal tip cells of the mutant. The rate of spindle elongation during anaphase B of mitosis was reduced 11%, but the rate was not significantly different from that of wild type. This lack of a substantial mitotic phenotype is consistent with the primary role of the conventional kinesins in organelle motility rather than mitosis. Our results provide further evidence that the microtubule-based motility mechanism has a direct role in apical transport of secretory vesicles and the first evidence for its role in apical transport of mitochondria in a filamentous fungus. They also include a unique demonstration that a microtubule-based motor protein is essential for normal positioning of the Spitzenkörper, thus providing a new insight into the cellular basis for the aberrant hyphal morphology.
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