Thirteen families have been described with an autosomal dominantly inherited dementia named frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), historically termed Pick's disease. Most FTDP-17 cases show neuronal and/or glial inclusions that stain positively with antibodies raised against the microtubule-associated protein Tau, although the Tau pathology varies considerably in both its quantity (or severity) and characteristics. Previous studies have mapped the FTDP-17 locus to a 2-centimorgan region on chromosome 17q21.11; the tau gene also lies within this region. We have now sequenced tau in FTDP-17 families and identified three missense mutations (G272V, P301L and R406W) and three mutations in the 5' splice site of exon 10. The splice-site mutations all destabilize a potential stem-loop structure which is probably involved in regulating the alternative splicing of exon10. This causes more frequent usage of the 5' splice site and an increased proportion of tau transcripts that include exon 10. The increase in exon 10+ messenger RNA will increase the proportion of Tau containing four microtubule-binding repeats, which is consistent with the neuropathology described in several families with FTDP-17.

Mutations in microtubule-associated protein tau recently have been identified in familial cases of frontotemporal dementia (FTD). We report the frequency of tau mutations in a large population-based study of FTD carried out in the Netherlands from January 1994 to June 1998. Thirty-seven patients had >/=1 first-degree relative with dementia. A mutation in the tau gene was found in 17.8% of the group of patients with FTD and in 43% of patients with FTD who also had a positive family history of FTD. Three distinct missense mutations (G272V, P301L, R406W) accounted for 15.6% of the mutations. These three missense mutations, and a single amino acid deletion (DeltaK280) that was detected in one patient, strongly reduce the ability of tau to promote microtubule assembly. We also found an intronic mutation at position +33 after exon 9, which is likely to affect the alternative splicing of tau. Tau mutations are responsible for a large proportion of familial FTD cases; however, there are also families with FTD in which no mutations in tau have been found, which indicates locus and/or allelic heterogeneity. The different tau mutations may result in disturbances in the interactions of the protein tau with microtubules, resulting in hyperphosphorylation of tau protein, assembly into filaments, and subsequent cell death.

The induction of glucose oxidase, catalase, and lactonase activities was studied both in wild-type and in glucose oxidase regulatory and structural mutants of Aspergillus niger. The structural gene for glucose oxidase was isolated and used for Northern analysis and in transformation experiments using various gox mutations. Wild-type phenotype could be restored in the glucose oxidase-negative mutant (goxC) by transformation with the structural gene. We conclude, therefore, that the goxC marker which is located on chromosome 2 represents the structural gene of glucose oxidase. Glucose and a high oxygen level are necessary for the induction of all three enzyme activities in the wild-type strain and it was shown that both glucose and oxygen effects reflect regulation at the transcriptional level. The goxB mutation results in constitutive expression of all three activities although modulated to some extent by the carbon source. The goxE mutation only has an effect on lactonase and glucose oxidase expression and does not relieve the necessity for a high oxygen level. Catalase and lactonase could not be induced in the glucose oxidase-negative strain (goxC). Addition of H2O2 resulted in the induction of all three enzymes in the wild-type without glucose being present. The H2O2 induction is probably mediated by the goxB product. Besides the H2O2 induction there is still an effect of the carbon source on the induction. A model for induction of glucose oxidase, catalase, and lactonase in A. niger is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Integration host factor (IHF), which is a histone-like protein, has been shown to positively regulate transcription in two different ways. It can either help the formation of a complex between a transcription factor and RNA polymerase or it can itself activate RNA polymerase without the involvement of other transcription factors. In this study, we present a third mechanism for IHF-stimulated gene expression, by counteracting the repression by another histone-like protein, H-NS. The early (Pe) promoter of bacteriophage Mu is specifically inhibited by H-NS, both in vivo and in vitro. For this inhibition, H-NS binds to a large DNA region overlapping the Pe promoter. Binding of IHF to a binding site just upstream of Pe alleviates the H-NS-mediated repression of transcription. This same ihf site is also involved in the direct activation of Pe by IHF. In contrast to the direct activation by IHF, however, the alleviating effect of IHF appears not to be dependent on the relevant position of the ihf site on the DNA helix, and it also does not require the presence of the C-terminal domain of the alpha subunit of RNA polymerase. Footprint analysis shows that binding of IHF to the ihf site destabilizes the interaction of H-NS with the DNA, not only in the IHF-binding region but also in the DNA regions flanking the ihf site. These results suggest that IHF disrupts a higher-order nucleoprotein complex that is formed by H-NS and the DNA.

Transcription initiation in Escherichia coli is influenced by promoter architecture and by the presence of regulatory proteins, which can either stimulate or repress this process (for a review, see reference 6). A classical E. coli promoter contains the Ϫ35 and Ϫ10 elements; both the sequence and the spacing of these elements are important determinants for promoter strength. Sequences upstream of the Ϫ35 element can increase promoter activity (2, 5). It was shown in the rrnB P1 promoter that sequences between Ϫ40 and Ϫ60 (the so-called UP element) increase transcription by interacting with the alpha subunit of RNA polymerase (12, 33). Mutant RNA polymerase, lacking the C-terminal domain of the alpha subunit (␣CTD), was unable to contact the UP element, and subsequently, transcription from the rrnB P1 promoter was less efficiently initiated (33). The ␣CTD is a distinct domain of 64 amino acids which can dimerize and bind the DNA (3). The structure of this domain has been solved by nuclear magnetic resonance (21). By using the alanine scan method, in which every amino acid of two regions of the ␣CTD one by one was exchanged for an alanine, the residues at positions 265, 268, 269, 296, 298, and 299 were identified as important for UP-element binding (12).A number of bacterial activators which generally bind to a site close to the promoter and which stimulate the initiation of transcription have been identified (20). Of these activators, the cyclic AMP receptor protein (CRP) is the best studied (reviewed in reference 23). Two classes of promoters stimulated by CRP can be distinguished (20). For class I promoters, with the CRP binding site located upstream of the Ϫ35 element, most frequently around position Ϫ61, contacts have been found between the activator and the alpha subunit of the RNA polymerase complex. Mutation and cross-linking studies revealed that the target for CRP interaction also resides in the ␣CTD (7,47,48). An alanine scan identified glutamic acid 261 as one of the most important residues for this contact (37). In class II promoters, the CRP binding site is located around position Ϫ41 where it overlaps with the classical Ϫ35 promoter element. Although CRP bound at such a site makes contact with the alpha subunit, mutant RNA polymerase lacking the ␣CTD is still activated by CRP (1,45,47).