Two divergent types of nerve pathology in patients with different P0 mutations in Charcot-Marie-Tooth disease.

In seven unrelated patients with a demyelinating motor and sensory neuropathy, we found mutations in exons 2 and 3 of the P0 gene. Morphologic examination of sural nerve biopsy specimens showed a demyelinating process with onion bulb formation in all cases. In four patients, ultrastructural examination demonstrated uncompacted myelin in 23 to 68% of the myelinated fibers, which is in agreement with the widely accepted function of P0 as a homophilic adhesion molecule.

Deletion of the serine 34 codon from the major peripheral myelin protein P0 gene in Charcot-Marie-Tooth disease type 1B.

Charcot-Marie-Tooth disease type 1B (CMT1B) is genetically linked to chromosome 1q21-23. The major peripheral myelin protein gene, P0, has been cloned and localized to the same chromosomal region. P0 is a 28 kDa glycoprotein involved in the compaction of the multilamellar myelin sheet and accounts for more than half of the peripheral myelin protein content.

A system to study transcription by yeast RNA polymerase I within the chromosomal context: functional analysis of the ribosomal DNA enhancer and the RBP1/REB1 binding sites.

We have developed a novel system to study transcription by yeast RNA polymerase I (Pol I) of mutated rDNA units within the chromosomal context. For this, complete rDNA units carrying specific oligonucleotide tags in both the 17S and 26S rRNA genes were integrated into the chromosomal rDNA locus. Using this novel system, we analysed the action of the rDNA enhancer in stimulating transcription within the chromosomal context.

The yeast RNA polymerase I promoter: ribosomal DNA sequences involved in transcription initiation and complex formation in vitro.

Using an in vitro transcription system for Saccharomyces cerevisiae RNA polymerase I, we have analyzed Pol I promoter deletion mutants and mapped the boundaries of the promoter between positions -155 and +27. The 5'-boundary of the minimal core promoter capable of transcription initiation, however, was found to lie between -38 and -26. The 3'-deletion extending to -2 and -5 still allowed some transcription, suggesting that the positioning of Pol I is directed by upstream sequences.

A yeast ribosomal DNA-binding protein that binds to the rDNA enhancer and also close to the site of Pol I transcription initiation is not important for enhancer functioning.

Using the gel retardation assay we have identified a protein that can specifically bind to a site within the enhancer of the 37S pre-ribosomal RNA operon in yeast, as well as to a site 210 bp upstream of the site of transcription initiation of this operon. This protein (RBP1) has been partially purified by means of heparin-agarose chromatography and protects 20 bp in the rDNA enhancer, and 25 bp in the initiation region, against DNase I in an in vitro footprinting assay. In vivo footprinting studies using methylation of intact yeast cells with dimethylsulphate, indicate that the same binding sites are occupied in vivo as well.