Flagellar dynein was discovered over 30 years ago as the first motor protein capable of generating force along microtubules. A cytoplasmic form of dynein has also been identified which is involved in mitosis and a wide range of other intracellular movements. Rapid progress has been made on understanding the mechanism of force production by kinesins and myosins. In contrast, progress in understanding the dyneins has been limited by their great size (relative molecular mass 1,000K-2,000K) and subunit complexity. We now report evidence that the entire carboxy-terminal two-thirds of the 532K force-producing heavy chain subunit is required for ATP-binding activity. We further identify a microtubule-binding domain, which, surprisingly, lies well downstream of the entire ATPase region and is predicted to form a hairpin-like stalk. Direct ultrastructural analysis of a recombinant fragment confirms this model, and suggests that the mechanism for dynein force production differs substantially from that of other motor proteins.

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We have characterized a soybean gene cluster that encodes a group of auxin-regulated RNAs (small auxin up RNAs). DNA sequencing of a portion of the locus reveals five homologous genes, spaced at intervals of about 1.25 kilobases and transcribed in alternate directions. At least three of the genes are transcriptionally regulated by auxin. An increase in the rate of transcription is detected 10 min after application of auxin to soybean elongating hypocotyl sections. Each of the genes contains an open reading frame that could encode a protein of 9 kilodaltons to 10.5 kilodaltons. Sequence comparisons among the five genes reveal several areas of high homology. Two regions of high homology begin about 250 base pairs upstream of the open reading frames and two regions of homology have been identified in sequences downstream of the open reading frames. One of the latter sequences occurs in the 3'-untranslated region of the RNAs. The other occurs far downstream, 618 base pairs to 741 base pairs from the stop codon. Conservation of these sequences among the five different genes suggests that they may be important for the regulation of expression of the genes.

It is generally believed that patients with primary generalized epilepsy have normal cognition and neuroimaging studies. We have previously shown that patients with juvenile myoclonic epilepsy (JME) have impaired visual working memory. In this study we examined relative regional changes in 18FDG uptake during a visual working memory paradigm in patients with JME. At rest, there were regional decreases in relative glucose uptake compared to controls. Unlike control subjects, increased activity in the dorsolateral prefrontal cortex was not found during the working memory task. Other regions with increased uptake in controls, such as premotor cortex and basal frontal cortex, also showed no increases, whereas medical temporal structures appeared to play a role in JME but not in control subjects' task performance. The data suggest that JME, a type of primary generalized epilepsy, may suffer from cortical disorganization that affects both the epileptogenic potential and frontal lobe cognitive functioning.

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